Winlogon.exe memory could not be "written"

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Hello,

first of all, sorry about my english, I hope you could read it.
I'm an administrator for over 200 PC's and I get on random computers
the
following error message:

Application: winlogon.exe ... error memory could not be "written"

winlogon.exe - Fehler in Anwendung: Die Anweisung in "0x74e740c3"
verweist auf Speicher in "0x00000000". Der Vorgang
"written" konnte nicht auf dem Speicher durchgeführt werden.

This error occurs before the user can logon. After restarting pc the
error don't occur again. Even if you start the computer 10 times, the
error occurs very randomly and I couldn't
reproduce it controlled.

I´m getting the error since 3 Weeks and I haven't found
any solution.

I checked for viruses and trojans, nothing found.
I have installed Hotfixes and Patches to the av-scanner.

Windows 2003 Domain
Windows XP with SP2 (all MS-Hotfixes installed)
Trend Micro Officescan V 7.0
Office XP with Outlook 2003
and more.. but this software is installed on all pc's

Is there a way to find out which software causes the fault?

Thanks for any help or usefull comments.

Thank you
Christian Feneberg
===============
MCP, MCSA+S, MCSE+S

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