ENTU Entrust (MM)

------------------------- --------------------
CUSIP NO. 293848107 SCHEDULE 13D PAGE 2 OF 7 PAGES
------------------------- --------------------

-------------------------------------------------------------------------------
 1 NAME OF REPORTING PERSON
 I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY)

 Arnhold and S. Bleichroeder Advisers, LLC
-------------------------------------------------------------------------------
 2 CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP* (a) [ ]
 (b) [ ]

-------------------------------------------------------------------------------
 3 SEC USE ONLY

-------------------------------------------------------------------------------
 4 SOURCE OF FUNDS*

 AF, OO
-------------------------------------------------------------------------------
 5 CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT
 TO ITEMS 2(d) or 2(e) [ ]

-------------------------------------------------------------------------------
 6 CITIZENSHIP OR PLACE OF ORGANIZATION

 Delaware
-------------------------------------------------------------------------------
 7 SOLE VOTING POWER

 3,200,000
 ---------------------------------------------------------
 NUMBER OF 8 SHARED VOTING POWER
 SHARES
BENEFICIALLY -0-
 OWNED BY ---------------------------------------------------------
 EACH 9 SOLE DISPOSITIVE POWER
REPORTING
PERSON WITH 3,200,000
 ---------------------------------------------------------
 10 SHARED DISPOSITIVE POWER

 -0-
-------------------------------------------------------------------------------
 11 AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH PERSON

 3,200,000

-------------------------------------------------------------------------------
 12 CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES
 CERTAIN SHARES*
 [ ]
-------------------------------------------------------------------------------
 13 PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

 5.2%
-------------------------------------------------------------------------------
 14 TYPE OF REPORTING PERSON*

 IA
-------------------------------------------------------------------------------
 * SEE INSTRUCTIONS BEFORE FILLING OUT!

------------------------- --------------------
CUSIP NO. 293848107 SCHEDULE 13D PAGE 3 OF 7 PAGES
------------------------- --------------------


ITEM 1. SECURITY AND ISSUER.

 This statement on Schedule 13D relates to the Common Stock, $0.01 par
value per share (the "Shares"), of Entrust, Inc. (the "Issuer"). The principal
executive office of the Issuer is located at One Lincoln Center, Suite 1340,
5400 LBJ Freeway, Dallas, TX 75240.


ITEM 2. IDENTITY AND BACKGROUND.

 (a) This statement is filed by Arnhold and S. Bleichroeder Advisers,
LLC, a Delaware limited liability company and an investment adviser registered
under the Investment Advisers Act of 1940 (the "Reporting Person"). The Shares
reported herein are held by various clients in accounts under the Reporting
Person's management and control. Messrs. Jason Dahl and Jonathan Spitzer
(together, the "Portfolio Managers") are co-portfolio managers for these client
accounts and, as such, have the authority to make decisions regarding the voting
and disposition of the Shares. Mr. John P. Arnhold (the "Principal") is the
Chairman and Chief Executive Officer of the Reporting Person.

 (b) The principal business address of the Reporting Person, the
Principal and the Portfolio Managers is 1345 Avenue of the Americas, New York,
New York 10105.

 (c) The principal business of the Reporting Person, the Principal and
the Portfolio Managers is investing for client accounts under their management.

 (d) None of the Reporting Person, the Principal or either of the
Portfolio Managers has, during the last five years, been convicted in a criminal
proceeding (excluding traffic violations or similar misdemeanors).

 (e) None of the Reporting Person, the Principal or either of the
Portfolio Managers has, during the last five years, been a party to a civil
proceeding of a judicial or administrative body of competent jurisdiction and as
a result of such proceeding was or is subject to a judgment, decree or final
order enjoining future violations of, or prohibiting or mandating activities
subject to, federal or state securities laws or finding any violation with
respect to such laws.

 (f) The Principal and the Portfolio Managers are citizens of the United
States of America.


ITEM 3. SOURCE AND AMOUNT OF FUNDS OR OTHER CONSIDERATION.

 The Shares reported herein were acquired at an aggregate purchase price
of approximately $6.1 million. Such Shares were acquired with investment funds
in client accounts under the Reporting Person's management and, in certain
cases, were purchased on margin.


ITEM 4. PURPOSE OF TRANSACTION.

 The Reporting Person originally acquired Shares for investment purposes
in the ordinary course of business, subsequent to the announcement on April 13,
2009 of the definitive agreement by the Issuer to be acquired by an affiliate of
Thoma Bravo, LLC ("Thoma Bravo"). On June 18, 2009, the Reporting Person
delivered a letter to the Board of Directors of the Issuer (the "June 18
Letter") stating that it intended to vote its eligible shares against the
adoption of the Thoma Bravo merger agreement for the reasons set forth in the
June 18 letter.

------------------------- --------------------
CUSIP NO. 293848107 SCHEDULE 13D PAGE 4 OF 7 PAGES
------------------------- --------------------

A copy of the June 18 Letter is attached as Exhibit A hereto and is incorporated
by reference.

 Except as set forth herein, or as would occur upon completion of any of
the actions discussed herein, the Reporting Person has no present plan or
proposal that would relate to or result in any of the matters set forth in
subparagraphs (a)-(j) of Item 4 of Schedule 13D. The Reporting Person intends to
review its investment in the Issuer on a continuing basis and may engage in
discussions with management, the Board of Directors, other shareholders of the
Issuer and other relevant parties concerning a potential acquisition of the
Issuer, and potentially concerning other matters with respect to the Reporting
Person's investment in the Shares, including, without limitation, the business,
operations, governance, management, strategy and future plans of the Issuer.
Depending on various factors, including, without limitation, the terms of any
transaction that may be proposed, the Issuer's financial position and strategic
direction, the outcome of any discussions referenced above, actions taken by the
Board of Directors, price levels of the Shares, other investment opportunities
available to the Reporting Person, conditions in the securities market and
general economic and industry conditions, the Reporting Person may in the future
take such actions with respect to its investment in the Issuer as it deems
appropriate, including, without limitation, purchasing additional Shares or
selling some or all of its Shares, engaging in short selling of or any hedging
or similar transactions with respect to the Shares and/or otherwise changing its
intention with respect to any and all matters referred to in Item 4 of Schedule
13D.


ITEM 5. INTEREST IN SECURITIES OF THE COMPANY.

 (a) As of the close of business on June 17, 2009, the Reporting Person
is deemed to be the beneficial owner of 3,200,000 Shares, constituting
approximately 5.2% of the Shares outstanding. The aggregate percentage of Shares
reported herein is based upon 61,562,965 Shares outstanding, which is the total
number of Shares outstanding as of May 5, 2009 as reported in the Issuer's
Quarterly Report on Form 10-Q filed on May 11, 2009 for the period ended March
31, 2009.

 (b) By virtue of investment management agreements with its clients, the
Reporting Person has sole voting and dispositive powers over the 3,200,000
Shares reported herein, which powers are exercised by the Principal and the
Portfolio Managers.

 (c) Information concerning transactions in the Shares effected by the
Reporting Person during the past sixty days is set forth in Schedule A hereto
and is incorporated herein by reference. All of the transactions in Shares
listed on Schedule A hereto were effected in the open market.

 (d) Clients of the Reporting Person have the right to receive and the
ultimate power to direct the receipt of dividends from, or the proceeds of the
sale of, the Shares reported herein.

 (e) Not applicable.

------------------------- --------------------
CUSIP NO. 293848107 SCHEDULE 13D PAGE 5 OF 7 PAGES
------------------------- --------------------

ITEM 6. CONTRACTS, ARRANGEMENTS, UNDERSTANDINGS OR RELATIONSHIPS WITH
 RESPECT TO SECURITIES OF THE COMPANY.

 Except as otherwise set forth herein, the Reporting Persons do not have
any contract, arrangement, understanding or relationship with any person with
respect to the securities of the Issuer.


ITEM 7. MATERIAL TO BE FILED AS EXHIBITS.

Exhibit A - Reporting Person's letter to the Issuer dated June 18, 2009.

------------------------- --------------------
CUSIP NO. 293848107 SCHEDULE 13D PAGE 6 OF 7 PAGES
------------------------- --------------------


 SIGNATURES

 After reasonable inquiry and to the best of my knowledge and belief, I
certify that the information set forth in this statement is true, complete and
correct.

Dated: June 18, 2009

 ARNHOLD AND S. BLEICHROEDER ADVISERS, LLC

 By: /s/ Mark Goldstein
 ----------------------
 Name: Mark Goldstein
 Title: Senior Vice President

------------------------- --------------------
CUSIP NO. 293848107 SCHEDULE 13D PAGE 7 OF 7 PAGES
------------------------- --------------------


 SCHEDULE A

TRANSACTIONS IN THE SHARES BY THE REPORTING PERSON DURING THE PAST 60 DAYS

Date of Transaction Shares Purchased (Sold) Price Per Share ($)
------------------- ----------------------- -------------------
 04/20/09 215,000 1.87
 04/21/09 285,857 1.87
 04/22/09 126,979 1.89
 04/23/09 53,000 1.88
 04/27/09 209,459 1.91
 04/28/09 45,159 1.90
 04/29/09 12,930 1.91
 04/30/09 200,000 1.91
 05/04/09 52,586 1.91
 05/05/09 76,766 1.89
 05/07/09 49,547 1.88
 05/07/09 52,900 1.89
 05/08/09 30,000 1.90
 05/11/09 92,453 1.89
 05/13/09 375,000 1.89
 05/14/09 283,000 1.90
 05/14/09 1,000 1.89
 05/15/09 147,900 2.10
 05/15/09 1,000 1.95
 05/21/09 10,800 2.07
 05/22/09 18,800 2.06
 05/26/09 40,600 2.07
 05/27/09 28,000 2.07
 05/28/09 185,300 2.06
 05/29/09 108,600 2.05