Symptoms
Sessions appear to freeze or hang (in other words, the sessions do not respond to mouse or keyboard input) when using certain applications that use a large amount of GUI resources in sessions with corresponding large display resolutions and high color depths.
This may also be more evident in multiple-monitor environments, where display resolutions are typically larger and have higher color depths.
Additionally, depending on how an application is written, it may report an error to the effect that it is experiencing some kind of drawing failure.
For example:
Microsoft Office PowerPoint 2007 may not display consistently at the maximum session size of 1930x1447 at 24-bit color.
The Windows Picture & Fax Viewer may not display consistently with resolutions sizes larger than 1600x1200 at 24-bit color.
Note: The workarounds listed in this article may also apply to all the supported versions of Presentation Server running on a Windows 2003 Terminal Services platform.
Cause
You may have reached the default per-user session memory limit in Windows Server 2003.
In Presentation Server 4.5, more memory can be used for drawing large, high-detail bitmaps than in previous versions. As a result, the default Windows per-user session memory limit may be reached sooner than in previous versions of Presentation Server.
Workaround
The following workarounds are suggested at this time.
Aside from manually disconnecting and reconnecting to a session to recover the session, use smaller session resolution sizes.
-Or-
WARNING! Using Registry Editor incorrectly can cause serious problems that may require you to reinstall your operating system. Citrix cannot guarantee that problems resulting from the incorrect use of Registry Editor can be solved. Use Registry Editor at your own risk.
For a more permanent solution, increase the SessionPoolSize through the SessionPoolSize registry entry.
See Microsoft Knowledge Base article 840342 for complete details and usage.
After adjusting the SessionPoolSize, the symptoms documented above with PowerPoint and the Windows Picture & Fax Viewer are no longer seen.
More Information
The default Windows Server 2003 per-user session limit is 16 megabytes (MB) to 32 MB for a 32-bit server and 64 MB for a 64-bit server.
This issue is tracked through Citrix Problem Report (CPR) numbers 158066 and 158351.

Source

__________________
PSP

>> Sessions that Use Large Amounts of Memory Become Unresponsive