Can't help on the Vista drivers. But I had a problem once with the calibration on the TM-868 working fine, until I loaded the game. The problem was the drivers didn't adjust the calibration when the game changed the desktop resolution, so the calibration in the game was off. The 'fix' was to set the windows desktop to the same res as the game when calibrating it. After calibration I think you can change it back to what you want. Then when the game changes the res, the touchscreen was calibrated ok. That may work if that's your problem.
I did hear back from Dodger, and he is having difficult problems with the server, so has decided to go back to a US Host server soon. Not sure on a date, but maybe in a few days. Then you can post this there or search the site for your answer...
WBK