I have a problem that affects all users.
Previously, when all my users on the 22.0/24 network opened Windows Explorer and clicked on "network", they could browse for the fileservers on the 1.0/24 network and the 1.0/24 network. On September 20, 2013 (just after a wireless network upgrade, incidentally), all browsing of the 1.0/24 file servers stopped. All 22.0/24 devices can still be seen.
None of the network discovery settings have changed for any computers, so far as I know.
All Windows security updates are automatically applied.