Choppy HD video playback - FCP X

So,

I am trying to work on a music video project, downloaded the trial version of FCP X, and am importing 1080p AVCHD videos (60 fps). When editing the video, any time I playback it runs really choppy. I am running a 15" MBP, from 2009 I believe. It has the 2.66GHz dual core i7, 8GB DDR3 installed, and the 330M (512mb) graphics card. I mean, my computer knowlege tells me that this SHOULDNT be happening. I've run similar setups on older computers without issues with choppy video, so I'm looking for an answer. Also, whenever I just play the videos back (in like VLC or something) they play completely fine. Anyways, please help!!!

Steve