This is so frustrating, I have many Arduino boards. Mostly Nano's. I have been using them on both win7 and win 8.1.
Today Oct 1. 2014 Many of them just stopped being recognized by my computers. Thus some work and some do not. On both win 8.1 laptop and on win 7 desktop.
When a good one is connected it makes the beep, and connects as com port XX in the computer device manager.
When a bad one is connected it makes the beep (on win 7 a bad beep) and the device manager show it as
Other Device
! FT232R USB UART (obviously not working)
It's like the driver just expired, and that there is some internal difference to the units.
Anybody else seen this issue?
Any insight to the cause, besides my wild guess.
Any idea's on solutions.Before it is suggested, I have been using the latest 8.1 drivers (signature is valid for win

and have tried uninstalling a failed unit, then reinstalling it and it just say no driver found for the device. Yet the good ones continue to work.
So far it has been Nano's that have not worked. Uno, mega and 3 of my Nano's still work.
I did a search and only found 1 thread that sounded the same, it was on in French, I used Google translator on the page and no real suggestion has been found yet.
A customer had bought a bunch of Nano's it seems like they are the ones that died, I probably got one of his in my stack.
Highflier