1. Making the assumption (at this point) that it's not hardware failure.....
2. Something I've experienced in the many years I've been doing what I've been doing is; sometimes the "mounted devices" in your registry gets "buggered"
WARNING: EDITING ONE'S REGISTRY IS TO BE TAKEN SERIOUSLY! YOU CAN CAUSE SERIOUS SYSTEM INSTABILITY IF YOU DO THE WRONG THING IN THE REGISTRY!
Now......with that warning out of the way........hehe
under HKLM >> SYSTEM >> MOUNTED DEVICES
You will see a list of every "mounted" drive/partition and their related DOS drive-letters. This list will include references for every drive (including every removable) drive you have and ever have had connected to your system. You will notice that every "DosDevice" letter has a corresponding "string" entry somewhere above it in the list.
When I've encountered an issue such as yours on systems through the years, I've simply matched-up all of the drives I have in my system (OS, etc.) with their strings above in the list and then carefully deleted the other entries. Any new removable drives you connect from that point forward will be once again "auto-detected" and correctly configured. Reboot your machine after deleting the "orphaned" entries and you should be in business!
The issue you're describing often happens in corporate environments where people have cause to connect/disconnect from mapped network drives while using removable USB keys etc.
My tip above, has worked without fail in all of those cases.
Of course if it's hardware failure we're looking at here......then my tip won't help.
AGAIN.......be very very careful when you're in the registry!!!