Applications crash when SpeedScreen enabled

On a Windows 2003 Server with SP1 running Citrix Presentation Server 4.0, after enabling SpeedScreen latency reduction (particularly "Local Text Echo") you may discover that many or all applications may stop working. Symptoms can include applications not opening, crashing immediately after launch, or simply a blank desktop (explorer.exe has crashed) if working with a published desktop. You may also see errors in the Application event log similar to one of the following:

Event Type: Error
Event Source: Application Error
Event Category: (100)
Event ID: 1000
Date: m/d/yyyy
Time: <time>
User: N/A
Computer: SERVERNAME
Description:
Faulting application <executable>, version <version>, faulting
module zlc_api.dll, version 4.0.2198.1, fault address <address>.

- or -

Event Type: Information
Event Source: Application Error
Event Category: (100)
Event ID: 1004
Date: m/d/yyyy
Time: <time>
User: N/A
Computer: SERVERNAME
Description:
Reporting queued error: faulting application <executable>, version
<version>, faulting module zlc_api.dll, version 4.0.2198.1, fault
address <address>.

This is caused by a conflict between SpeedScreen and the new Data Execution Prevention (DEP) features in Windows 2003 SP1. zlc_api.dll (the SpeedScreen API) intercepts information from the application. DEP is interfering with the proper operation of SpeedScreen, which then causes any executable attempting to use SpeedScreen to stop functioning.

Citrix has identified numerous problems with Windows 2003 SP1, including a document which offers a hotfix for this issue for Presentation Server 3.0 only. Information on this issue under Presentation Server 4.0 is unfortunately limited.

One resolution for this issue is to disable DEP on the affected server. To do this you must modify to the boot.ini file. WARNING: Incorrectly changing the boot.ini file can render your system unbootable. You should only make these changes if you know what you are doing and understand you make them at your own risk.:

Click Start -> Control Panel -> System
On the Advanced tab, click the Settings button under Startup and Recovery
Click the Edit button
Change the NoExecute boot option to read /NoExecute=ALWAYSOFF
Save your changes and close the window
You must reboot for the new DEP setting to take effect

For more information on DEP, please see Microsoft support article 875352.

Author: ASAK
Created: Apr 6 2006
Categories: Citrix Metaframe/Presentation Server
TechByte #130

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