flashing green frames during playback in After Effects
 

I've been working with C300 footage in Premiere and wanted to test the limits of the codec in AE, so I brought it in. At first, everything was fine. Then I started seeing green frames every other frame during playback. I've seen this kind of thing intermittently with my old XH-A1 but the problem always resolved itself. I'm assuming it has something to do with the codec but I haven't been able to find other people having this problem.

I'm using a 2010 quad-core Mac Pro with the ATI Radeon HD 5770. I have 10GBs of RAM.