group of a committed file

[vbkal]

hello,

I have a problem with our CVS system. If someone commits a file with WinCVS, they get this :
-rwxrwx--- USR USR file1.
Every hour a script changes the group to :
-rwxrwx--- USR GROUP file1.

What I don't understand : if a person commits file1, then each time the files group is set back to USR. Why is that? Why doesn't the group stay on GROUP?

thx for the help.