King's Bounty: Armored Princess issue

[metiu]

Hello

I've got big problem with KB: Armored Princess. During the play game suddenly freezes for few seconds (scene is cut with multiple colorful diagonal short stripes) and then all graphic is switching off (game is working, cursor is on screen, I can move/cast spells, but all scene is black - and not only in the game, but also in menu (Princess is visible but everything behind her is black)). After I quit to desktop there is an exclamation mark in my tray, but I can't open it. I thought it was hardware error, but I tested my hardware and everything is working just fine. What's more irritating - exclamation mark is not turning off until I restart my computer (even logging off is not working). This error isn't regular, but happens randomly.This kind of bugs doesn't appear in other games. What is happening?

My computer:
Windows Vista SP2 (with all possible updates)
Core 2 Duo 2,6 GHz
4GB RAM
ATI HD 4850 512 MB

Best regards
Mateusz

Edit: One more thing. Exclamation mark is affecting also on Windows Vista also. After quiting game - if UAC is asking for some permission, my monitor is showing monolithic colorful image which is disappearing after I cancel UAC (press ESC).