Hmm, that's very strange - could you send me a dxdiag file for the machine on which it doesn't work and your config.lua file which will be in the install directory. Also, if you know how, could you look and see if there is any error being reported in your OS's event viewer.
I'll then look into it further. I must say I've never even used Windows 7 let alone tested the game on it so it could well be a fundamental issue

I'll have to try and get hold of a copy.