File corruption when logging off

[dawks]

I've been fighting with this for a while now trying to figure out what the issue is. When a user on our network running Windows XP, logs off, Windows copies their files to our Windows Server 2003 box via roaming profiles. We've had many cases where the user gets a Delayed Write Failure message when logging off, and when they come back the next day and log in, their email (Outlook PST or Thunderbird) is corrupted. I think it has to do with users leaving everything open when they log off. This obviously shouldn't happen but something is causing it. Is there some kind of GPO I can change to prevent this?