FCP stutters on Animation clip playback.

FCP has been stuttering with clips on the play back. I have a series of Animation clips that are at most 6 sec long. whenever the play head gets to the third clip the canvas freezes but the playhead continues then a few clips later the canvas catches up with the playhead. These clips are originally exported from After Effects and brought into FCP. While in FCP there isn't any motion, filters, or effects added to the clip.

FCP 7.0.2, Mac OSX 10.6.3, 6GB Ram, Quadro FX 4800 18.5.2
Memory usage; Application 100% Still Cache 36%
Playback Control; RTafe, Video: Dynamic (we also tried low), Frame: full

Footage
Animation, 1920x 1080, Square Pixel Aspect, size 1.3GB

Thank you

Animation is a high data rate, processor intensive codec. It should not be used as an editing codec, but as an intermediate codec, specifically to carry an alpha channel. It's now be superseded by ProRes 4444 for FCP7 users, which is a real-time codec with alpha.

All the best,

Tom

Also, what kind of drive are you playing it off?