My Nokia Lumia RM-803 can not connect any more with my laptop nor with zune. It's detected as an unknow device in the device manager. I already tried to update the driver trough the device manager, but isn't working also.
Anyone can help, so I'm able to update my phone etc.
Welcome to the Nokia Forum!
Have you tried using another USB, USB port or PC to isolate the issue? You can also try to reboot the phone first and then connect it to the Zune software. Aside from updating your PC driver, have you tried the other steps provided on this link: http://support.microsoft.com/kb/2410180/en-us?