AT32UC3A usb driver Windows 7 64 bit

Hello all
I am trying to follow the description for updating firmware on the Wifi Shield.

But I am not able to connect to the shield using usb.

Device manager tells me:
The drivers for this device are not installed. (Code 28)
There is no driver selected for the device information set or element.
To find a driver for this device, click Update Driver.

I tried to browse for the driver in \Program Files (x86)\Arduino
but it does not find any suitable driver.

If someone can give me a hint about how to find and install the driver it would be great

Thanks in advance

/Per