Read Only Access Problem

I am recently getting reports of users unable to access files they could previuosly. They are receiving the message “file is open by another user or themselves, do you want to open in read only mode” This is not the exact message as it lists the user name in some cases. Also, not sure if this is related but, it started occurring about the same time. Temp files are being created mostly excel. These files “hang around” even after original has been closed. They cannot be deleted for several days. As background info, we have a Win2k Pro server and XP clients using M.S. Office 2k.

Any help would greatly appreciated,
Jay