Incidentally I think this has been a problem for a real long time of me being unable to map drives to servers - specifically my own Web Server.
Microsoft released its update to fix several identified vulnerabilities, including a remote execution flaw in Power Shell and to add robustness against side-channel attacks like those targeting the Meltdown and Spectre flaws.
But a number of users immediately complained of networking issues, with Microsoft confirming there are now three known problems with the January patch.
Note that you do have to make a change though for this to work. Clearly some application (which probably was uninstalled since) modified this setting, but nevertheless this is troublesome.
Further the Windows 8 troubleshooting applet was a complete loss, going straight into 'Do you have permissions?
Several other people have reported they've seen similar problems.
Empty entries, Lanman Workstations name truncated or mangled and even missing.Another wrote: "Everything was just fine – until this morning. I'm uninstalling updates now to test against that." Microsoft has advised customers experiencing a failed network interface controller to locate the device using 'scan for hardware changes' via device management, or automatically search for updated driver software.All workstations throwing an error trying to access shared drives on a 2008 server – The handle is invalid. But many said they had only been able to get around their networking issues by completely rolling back the January patch.To fix this I removed the two empty entries and moved Lanman Work Station to the front of the list and low and behold I get my login dialog back and was able to connect to the remote machine.Not sure how this got munged, but I suspect custom VPN clients have something to do with this.' - of course not since I was never prompted :-) If you don't know what the problem it's hard to come up with the solution - I was lucky to find that forum post earlier that pointed me in the right direction.