Complete firmware upgrade for every component of the server. BIOS, HDS, NICs, Etc. HP Server DL380 G4
Then:
http://support.citrix.com/product/xa/v5.0_2008/
http://support.microsoft.com/kb/949914 - Citrix ICA clients may crash when they are connecting to a Windows Server 2008-based terminal server that has Citrix Presentation Server installed
http://support.microsoft.com/kb/951149/en-us - Stop error on a Windows Server 2008-based terminal server when the server is running under a heavy load: 0×0000000A
http://support.microsoft.com/kb/955625 - Mandatory user profiles do not work as expected on Windows Vista-based and Windows Server 2008-based client computers when the %LogonServer% environment variable is set in the profile path
http://support.microsoft.com/kb/953531 - A 0×0000007E Stop error occurs in Windows Server 2008 after you unmount and delete a persistent VSS snapshot
http://support.microsoft.com/kb/958652 - Some Citrix commands do not work correctly in Citrix XenApp 5.0 for Windows Server 20083