We have seen several computers in our group lose their SolidWorks license, even though the SolidNetWork License Manager shows that they have a license in use.  This is a very sporadic, intermittent problem, and there does not seem to be anything in particular causing it.  Out of the 30 or so users, about 8-10 have seen this.  It happens for any of those users about twice a week.  There are two different dialogs - the first warns you that SolidWorks was unable to obtain a license.  The other will pop up later, usually 5 to 20 minutes, and inform you that you will be allowed to save your modified documents.  Once you OK the dialog, SolidWorks shuts down.  We often don't see the first one at all, though.  If you start the license manager utility when you see the dialog box pop up, it will show that your machine is currently using a license, at least according to the license server.  And, there is never any other indication of a network connectivity issue - no dropped network drives, connection errors, etc.

Our VAR's Tech Support has been looking into this, having us try various fixes, but nothing has helped so far.  We know it started on day one when we went to 2015.  We installed directly to SP3 from an Admin image, and have tried several things such as reinstallation, repair installs, settings changes, etc. on both the workstations and the server.

Has anyone else out there seen this issue?  More to the point, anyone have a fix?