Consider the following scenario:

This issue occurs because the non-administrator user account cannot access the %WINDIR%\System32 folder. By default, WPF writes the output file to the %WINDIR%\System32 folder. The %WINDIR%\System32 folder requires administrator permissions. When the non-administrator account tries to access this folder, the WPF caching code is triggered. This code causes the screen to flicker. 

In 32-bit versions of the Windows Server 2003 operating system, the output file is D3d9caps.dat. In 64-bit versions of the Windows Server 2003 operating system, the output file is D3d9caps64.dat.

To resolve this problem, install the following hotfix. After you install this hotfix, WPF applications write the output file to the current user profile instead of to the %WINDIR%\System32 folder.

See http://support.microsoft.com/kb/955692 for more details

• You use a non-administrator user account to connect to a Windows Server 2003-base terminal server by using a third-party terminal client, such as a Citrix ICA client.
• You run Windows Presentation Foundation (WPF) applications in the terminal server session.

In this scenario, you may notice that your screen flickers. You do not encounter this issue when you use Remote Desktop Connection (RDC) to create the terminal server session