do you have antivirus software?
maybe it is the antivirus software renaming files to keep them from opening if they are infected...
or...maybe it is just a virus...renaming the files.
you can go to <A HREF="http://housecall.antivirus.com/" target="_new">http://housecall.antivirus.com/</A>
and scan your computer for viruses...and i think that it might be able to clean the files if they are repairable.
this is an odd problem...
-Live, Learn, then build your own computer!-