While installing a new Citrix XenApp  farm for a customer I upgraded the servers to Hotfix Rollup Pack 7 (HRP7, PSE450W2K3R07). The XenApp 5 farm is build as virtual servers on a  VMWare vSphere 4.1 cluster. Installing Hotfix Rollup Pack 7 via RDP console session (mstsc /console) succeeded  with no error and the farm booted nicely after installing the HRP.

The troubles started when I tried to connect to the farm via an ICA connection, only few seconds after initiating the connection the selected server crashed with an 0x000000CF (TERMINAL_SERVER_DRIVER_MADE_INCORRECT_MEMORY_REFERENCE)BSOD. After the BSOD the server rebooted nicely but an ICA connection was never setup.

Investigating this problem led me to some specific solutions to the problem like:

  • Copying an older version of twexport.sys to “C:\Program Files\Citrix\Drivers” and “C:\Windows\System32\Drivers” [Source]
  • Installing hotfix PSE450R07W2K3011

but none of them solved my solved the problem. Eventually the problem was solved by installing HRP7 NOT via RDP BUT via the VMWare console