Also: Idiot russians that destroy gameplay by just taking the generator in Wave 20 and running into enemies...
Was it really so important to tell what nationality they were?
I tested the single player version and it worked fine on my side, played for 3 waves only (had no more spare time to test it).
My system: Win7 x64, AMD Athlon II X64 641 Quad-Core 2.80 GHz, 4 GB, AMD Radeon HD 6670
Best regards!