Game freezing every 10 seconds

I'm not sure if this qualifies as a legit question here, but I don't know where else to ask.

I have installed the Call of Duty 2 MAC version on my iMac. My system capabilities (RAM, processor, video) are way above the recommended requirements, so I would have expected the game to run smooth.

However, in-game, doesn't matter if I am in the main menu or playing, it keeps freezing for about 2 seconds, every 10 seconds or so. I have set the quality settings to maximum and minimum, and it's the same.

Clearly it has nothing to do with in-game quality settings, as it does this even while in the main menu.

Any idea what the problem might be? I suspect my computer (1.5 years old iMac, 2.7GHz i5, 8GB@1600MHz DDR3, GeForce GT 640M 512MB) has a problem... it does boot slower than when I bought it... and overall it's not as fast.