Your error is 0x50 and it cites pdcrypt1.sys which is an Encription Protcol Driver belonging to Citrix MetaFrame XP software by Citrix Systems. It was also blocking another Citrix Systems driver WDICA.sys from loading. It seems both these drivers have caused issues for many people.
Just F.Y.I.: http://forums.citrix.com/thread.jspa?threadID=73998