Heya,

Not sure of the exact issue, but generally good advise is to make sure your graphics drivers are up to date, and to use some or all of the following launch options to see if they help improve the performance:

Open the properties dialog for the game by right clicking the game's name in you game list. Click "SET LAUNCH OPTIONS". Try setting some or all of these launch options to reduce used graphics memory:
Windowed mode
-window

Reduced rendering quality
-fboQuality=3

Reduced texture quality
-textureQuality=3

I hope this helps!

Well, it's slightly more playable. Thanks b0ss