I've had 5 sleepless nights trying to find the cause of this problem. The only reason I even thought of OLD was because the last entry in the log was regarding OLD starting. That entry was about two hours before the lockup occured. The kicker is that the log shows the time that I hit the power button to be the time that the system locked up and not the time that I actually pushed the button. Sometimes its off by as much as 2 hours. I'm suspecting Black Screen Of Death syndrom since the windows system clock actually stops. The hardware clock is not affected and I can ping the server but no RDP or access via the console. The mailbox is also unaccessable. Once I stopped the scheduled OLD's the problem went away but soon I will have more problems if I can't defrag the databases. Anybody seen this before? I have Kaspersky installed but its be off since the first lockup. This is a Mailbox and Hub transport server. CAS is running on a separate server and there is no edge server yet.