Recently observed a couple users that couldn't create a new local file. What was unique about this situation was that they had shared the same laptop computer in the lab. I chose to have a few different students drive the computer that was connected to the projector so that they would get to do the work, the others could watch and I could get around the fact that I couldn't be part of their network.
Whenever I end up doing this it reminds me of my white glove days in various unionized cities where the local stagehands didn't permit you to do the work yourself, you just directed them to do everything, literally everything! Try doing your job all day long by telling someone else what to do, down to the slightest detail. Move case to here, open lid, remove the first cable, pull it over to the first lighting truss section, connect to the receptacle, coil the excess here in a clockwise rotation. Repeat for the next cable...over and over all day. You find out quickly how well you know your gig.
Back to the problem, when the users attempted to create new local files the next day the computer was still using the same Username for Revit but they were logged in as different computer users. When Revit saw that username was the same but the computer user that created the previous local file was different it balked and refused to save the file. When we changed the Revit username to something else, no problem.
Not very likely that others would encounter this but thought I'd share the oddity just in case.