we had this problem a couple of weeks ago DXD posted this reply and it worked
This issue typically occurs whenever a Service Pack is applied prior to networking support being installed. This is due to a file called SRV.SYS not being present when the Service Pack is installed and therefore the Service Pack does not install the updated version.
When you then install networking, the original SRV.SYS is installed and the problem occurs. If reinstalling the Service Pack could produce problems with other applications, you may want to just "expand srv.sy_" from the Serive Pack files and copy it to the System32 directory.
Good Luck