Read Only files

I have Windows 2000 Server Std being used as a File/Print server. Staff use
Office Products (Word/Excel 2000). Clients have full rights to their home
drive and able to open files fine, however when they go to save their work
the receive notice that file is "read only" and they must do a file, save-as
in order to save the file. If they wait for 30+ minutes they don't seem to
have a problem saving the file. Problem started about 3 weeks ago after
fully patching the server.

The Windows 2000 Server is fully patch and the workstations (windows 2000
and Windows XP) seem to have the problem even after fully patching the OS.