Why does my .pst file become corrupt after leaving computer on overnight?

This may because the LAN is accessing the PST and during the night if the computer goes to sleep the connection breaks between the user accessing PST over the LAN and keep PST in inconsitance state because the file is not closed properly by client. I cannot think of any other scenarios based on the information you provided..

Does this make sense to you?

First point of note is that Microsoft does not support the access of PST files over any form of network connection. It is well documented and causes file corruption.

From Microsoft...

"A .pst file is a file-access-driven method of message storage. File-access-driven means that the computer uses special file access commands that the operating system provides to read and write data to the file.

This is not efficient on WAN or LAN links because WAN/LAN links use network-access-driven methods, commands the operating system provides to send data to or receive from another networked computer. If there is a remote .pst (over a network link), Microsoft Outlook tries to use the file commands to read from the file or write to the file, but the operating system then has to send those commands over the network because the file is not on the local computer. This creates a great deal of overhead and increases the time it takes to read and write to the file. Additionally, the use of a .pst file over a network connection may result in a corrupted .pst file if the connection degrades or fails."


http://support.microsoft.com/kb/297019/en-us

Thanks for the feedback guys.  I understand the possible issues stemming from accessing the .pst over the LAN.  We have pushed the client to get a terminal server but they have declined.  There is only one user having this issue but all the users access their .pst over the LAN.  I suppose she could be the only one leaving her outlook open during the backup.  Any other feedback would be appreciated.

I recommend you to use Exchange Server instead, which is designed for client/server method. And in such a case, even if the locally cached .OST file(a file similar to .PST file that is used to store data) is corrupt), you can always rebuild it by re-sychnonize your client computer with the server.

Thanks for all your assistance.  The issue has temporarily been resolved.  The user does not seem to get the issue any longer.  I have stressed the needs for an Exchange server at this location.