File copied to network place is corrupt
 

Hi everybody,
I have a file server w2k with shared folders, and some users work with
office 2003 sp2 standard.
Well this users open a excel file in a share folder in my server and save
changes in this location, and close the file.
then when they open again the file, this is corrupt, I save the original
file in local hardisk and works fine,
What is the problem with this?
some body have a help?,.....thanks for your comments
Regards.