It's a long shot but I'd love to see info from your computer.
Could you download and install
USBDeview. Then plug your Kobo in and run the program.
Select ALL the devices (Ctrl-A) and then do a "Save Selected Items" (Ctrl-S) which will prompt you for a file name. Supply a name, and then after it's been saved, upload the txt file to the forums here.
I'm hoping to see some "extra" settings which might help us figure out what has happened.