I have recently built 5 Citrix Presentation Server 4.5 with Feature Pack 1 servers on Windows Server 2003, SP2. All 5 servers are experiencing random hang ups and are essentially freezing on a blank screen. No login screen, nothing at all. I have to do a hard shut down and when I log back onto the servers, there is nothing at all in the event logs to give me a clue as to why this is happening. I have searched the Citrix knowledge base and have found nothing relevant and since I have Feature Pack 1, the rollup package is unnecessary. Is there a Citrix or Microsoft hotfix out there that I am missing? These servers are all HP/Compaq Proliant servers and range from DL360's to DL380's ML350's, all G3 or above with a minimum of 4GB of RAM and all have dual processors and plenty of disk space. The user load on each server is averaging between 35 and 40 users concurrently throughout the day. Any help would be appreciated.