Arduino YUN unknown device error from windows USB


I have an arduino YUN which I've been using with my PC for a while and always worked just fine. I have the 1.5.5-r2 Arduino Software installed and drivers were also installed with it (sice I've been succesfully using my YUN). However I unplugged the YUN and plugged again and now I'm getting a "Unknown device" error from windows (usb port connection). My I've reset the YUN wifi and rst buttons successfully but keep getting the error. I've also tried the suggestions in other UNO florums here without success...
Does anyone know what to do? how to reinstall drivers or so?

BTW: My arduino UNO R3 is working without problems it seems to be the YUN only.

I'd appreciate any help provided