Editing a unit's GarminDevice.xml is useless if you let it reboot first as it's recreated and updated on each reboot by the unit itself. You need to downgrade to at least [Only registered and activated users can see links. ].
Remove any existing gcd file from the alpha's Garmin folder. Connect the alpha to your PC by USB in Mass Storage Mode. Drag the Alpha100_310.gcd to WebUpdater icon on your desktop to open it and follow the prompts. Read [Only registered and activated users can see links. ].
Warning: Be aware of the possible legal ramifications of using US frequency DCs in EU before you do this.
EDIT: See P#7 below for Fa_Piter's modded 3.1 file for easy downgrade.Code:Please Login or Register to see the links