Wanted to buy it, but demo locks up

[City Builder]

Hi,
I've been wanting to buy Kings Bounty TL since I enjoyed Heroes V so much, however I've installed the demo, and it locks up within about 5 minutes. And it's not just a normal game lock up where you can still return to the desktop, it's a hard lock where the only option is to power down the computer.

Im running the following:
Windows Vista 64 bit
Nvidia 8800GTS with the last driver (not the feb 2009 driver but the one before)
AMD Phenom 9500 or 9550 (I can't remember which)
8GB RAM
Plenty of Hard drive space (over 600GB free on the primary drive)

Is this a game and vista 64 bit issue or a driver issue or what? Obviously I don't wish to spend the money on a game that might or might not lock up my computer when I wish to play it.

Thanks,