Corrupt\duplicate user profiles

Does anyone have any info on a problem with users losing
their local settings because the system creates a new
profile when they logon? The profile will have a .000
or .001 etc. extension. It's as if the user just logged
in for the first time.

We have been having this problem very frequently at many
of our company's sites. Im trying to find out what causes
this to happen and how to fix it quickly.

If anyone has any information on this please let me know.

Thanks,
Jim