Excel files rename themselves

I have a computer running Vista home premium. It is working as the main storage computer for 2 other machines that access it's files. It appears to be randomly renaming files that have been opened. For example on file named "2011 finantial data" was being worked on and later, when I tried to open it again it no longer was in it's directory. Instead there was a file named "72B33600" When opened it was the correct file. This appears to be only Excell files but we seldom use anything else.

This problem started yesterday. I don't know if it is related but I also can't get several (15) Windows updates to install. A couple of the ones that won't update are KB2479628 and KB2393802.

I have run a full scan with AVG, I have done a SFC, I have tried the updates as administrator and tried installing them individualy. The updates don't concern me as much as the file name changes UNLESS they are a symptom of the problem.

 

Are you using the same version of Excel on all computers?

 

Yes Excell 2000