Access is denied

You might se the error Access is denied when some users start a published application or desktop from XenApp.

This issue can be seen on users who are member of an extended number of groups, there is not a specific number because it depends on the current number of users on the XenApp server.

You could lower the number of groups the users is a member of, or as a workaround you can increase the Kerboros MaxTokenSize.

On your XenApp server(s) create a dword value under HKLM\System\CurrentControlSet\Control\Lsa\Kerberos\Parameters and set the value 48000 (Decimal).

The servers must be restarted before the change will work.

http://support.citrix.com/article/CTX138329

http://support.microsoft.com/kb/938118/en-us