4.50 Update stuck on "loader loading screen"

Hi,

I have downloaded 4.50 via the Garmin Express tool and updated my G80 and it says now to switch it off and on to trigger/complete the update. It's currently stuck on the 'LOADER LOADING...' screen for the last 30 mins. Any ideas? This is my second attempt and same problem each time. I can reboot the device and it rolls back to 4.30.

Thanks!