Won't, compile, verify or brun bootloader.

as titel says my problem is that compiling or verifying get stuck at about 75% for hours without any error messages. Now i'we tested Burn Bootloader but it just says it cant find USB.

error message:

Arduino:1.6.7 (Windows 8.1), Kort:"Arduino/Genuino Uno"

avrdude: usbdev_open(): did not find any USB device "usb" Fel vid bränning av bootloader.

This report would have more information with "Show verbose output during compilation" enabled in File > Preferences.

COM5 is connected to the arduino/genuino board aswell.