You can spend a lot of time diagnosing faults like this. Re-installing drivers and such.
Have you tried that flash drive in another PC to check it isn't the drive that has failed? Have you tried more than one flash drive in that PC? If you are sure it isn't a problem with the drive then....
It could be caused by anything from hardware, something you have done, such as installing a new program, to malware of some kind.
As it was only 5 days ago I would advise you to make a restore point now, so you can return if needs be and then go back to a restore point set when it was all working. If that fixes the problem then I would make a new restore point and proceed from there. If that doesn't fix it then you could try an earlier restore point. But the fact you went back to a time when it worked kind of points to hardware.
I would also do rigorous anti Malware scans.
[navy]When I married "Miss Right" I didn't realise her first name was 'always'. LOL[/navy]