AVCHD Playback/editing buggy, slow, choppy

I’m able to import .mts files into CS4, and drop them on the timeline. They’ll play straight through once, but scrubbing through them, or even just hitting play in the middle of a clip, causes severe stuttering and sometimes a total lockup.

I know AVCHD is supposed to be more processor-intensive, but my machine is relatively new. What could be the problem?

Here’s my pc specs:

32-bit Vista

4Gb RAM

Nvidia Gforce 7 GTX vid card

Intel 2-Core Duo E8400 @3Ghz

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