Disapearing Queries And Reports

I've got several access databases located on our file server. Numerous users throughout the office have access to open and view them as has been the case for several years. Since the beginning of the year we have started seeing a brand new issue occur every couple of months in a few of our databases. One day everything will work fine, come in the next day and all of the macros, tables and most of the queries are gone. I have noticed when this happens the queries vanish in ascending alphabetical order, the first 2-10 or so may still be there but everything after that and in reports and macros are gone. Recently we've also had another access mdb start doing this problem and only one user other than the system administrator has access to that file, it is also located on the server and in a secured folder.

The only fix I've found is to restore from a tape backup from a few days before to confirm it's a good copy but this gets annoying.

Any thoughts as to the cause or solution?

All databases effected are located on a central server, get a nightly backup, have a list of tables almost completely made up of linked tables from multiple ms sql server 2000 databases. The files are Access2000 format.

Thank you in advance for your expertise, I'll add any furhter details you may want/need.