Overture in Ubuntu 10.04- doesn't run

[Zappanale]

I got Overture in the humble bundle, and after installing and playing it, although the menus and intro scene works fine, once the actual game starts (on the screen that says "I can look with left and right mouse buttons", etc) things turn sour. The entire screen is more or less one block of colour, a sort of light brown, and when I move the mouse it's incredibly jerky.

I have zero idea what's happening, and can provide whatever info is needed to fix it.

Thanks for any help you can give.