This may be the latest reason for this. I had this problem in the past and it started recently to occur again. Did I map any network drives? No. But what did happen, strange as it sounds was to boot up an old laptop that had mappings. I had noticed that two new mappings for that computer appeared when I open Exploder. The problem is that I can't delete the devices. Perhaps I'll have to turn on the old laptop and have it up and running for this PC to delete the network mappings. Sounds like **** but... It's Microsoft.
Also, this sounds a bit scary to just see these old mappings show up out of the blue. But after some thought I suppose it probably isn't that scary as I had authorized the computer in the past to access network shares. Just a reminder to remove sharing from old PCs when no longer using them. Something I'm sure that I will never remember to do.
In addition and a bit off-topic, if your problem is that file dates/time are no longer sorting correctly, make sure that the column is set to "Date Modified" and it hasn't been changed to simply "Date". I remember this happening from time to time with no explanation.