Cannot copy OCX file access denied

Hi,
I am using windows 2003 as a file server. I have shared folder where everybody can copy/modify/delete the file. But while someone is trying to overwrite an .ocx file it raise an error : "Cannot copy MSWINSOCK: Assess id denied. Make sure the disk is not full or write-protected and that the file is not currently in use".
But i ovserved that i can copy any ocx file except overwriting. In my Windows 2000 file server it does not make any error. It's only happening in windows 2003. Plz help me!!