Well, after much heartache, it appears we found the source of the problem. My excel file with vba code in it often gave a 'Document not saved' error when run/saved on a network drive. It didn't produce this error on a local drive.

The network drive in question was part of a RAID disk system (apparently this stands for Redundant Array of Inexpensive Disks). I am told that this disk system is not the on the actual server, but is run through the server.

Long story short, when the excel files in question were moved directly to the server's hard drive, the problem as gone. There is obviously some kind of conflict with excel/vba and the RAID disk setup.

While this is not a resolution (since we still don't know why we can use the RAID disks), we've moved the files to a direct location on the server and are now able to run the excel files normally.

Hope that helps someone out there. If anyone has discovered a solution for the RAID system, I'd love to know.

Thanks