Mario Kart- Gameplay is Slow

[tec_41]

Hello, I have downloaded a few games now and had very few issues- Super Mario Galaxy, Super Smash Bros, and a few others are running well. I just downloaded MarioKart and it looks great and isn't really choppy, but the playback is much slower then it should be. I get about 60% playback speed on average.

Is there something I should look to change? My computer is an i7 960 (not overclocked yet) with a gtx460 and 6gb of ram...Any help is appreciated!