Photoshop vs. Bamboo

Since a week now my Photoshop wrecks my Bamboo Tablet completely. I'm using CS4 and have a small postcard sized Bamboo. The tablet works fine with ALL applications but as soon as i change to photoshop it will only use the first 40% of the width of the tablet from the left side. with the rather bad resolution of the bamboo this is really annoying. I could fix it the first time by switching to the driver panel and changing the display projection but the fix never worked again...

i went back to the elder driver and it works like a charm again. funny enough the official wacom boards state you should disable windows own tablet pc additions to fix the issue but it doesn't help one bit...