This is the weirdest problem I have seen so far.

After inserting a USB stick, it shows in the device manager (with the correct name) but under "unknown devices", even though I used it before with no problems.

To solve this, I manually need to select a driver (in this case I choose  the standard disk driver), resulting in a code 10 (not able to start). Then I uninstall the device driver, scan for hardware changes, and the device reappears, with the correct driver, and it will function normally.

When I disconnect the device and then reconnect it (same or other USB port), I have to repeat the action mentioned above.

In the WER file that is created, the problem reported is "PnPDriverNotFound".Very strange since it loads correctly after installing a wrong driver and uninstalling it again.

Does anyone have a suggestion other then performing a reinstall ?

RC

I would start by checking the state of the OS by running a system file check (and DISM if nec)

Hi

In addition to what has been suggested by ZigZag, please check this USB stick on other Windows 8.1 machines, if it works properly on other machines, navigate to C:\Windows\Inf\usb.inf and C:\Windows\Inf\usb.PNF, back up them first and try to replace them with the same files from the healthy Windows 8.1 machine.

Regards,

D. Wu