There is a compatibility issue with Citrix XenApp Server when you are using DSA.
The issue occurs because Citrix XenApp Server and DSA call the same Microsoft library C:\PROGRA~2\Citrix\System32\mfaphook64.dll.
To resolve the issue:
- Apply the hot fix from this Citrix article: Hotfix Rollup Pack 2 for Citrix XenApp 6 for Microsoft Windows Server 2008 R2.
- Disable the Citrix API hooks by following the procedure from this Citrix article: How to Disable Citrix API Hooks on a Per-application Basis.