I was just about to post about what could potentially be the same issue.
Try removing sound from the timeline. For some reason, our copy of CS4 developed a bug after we upgraded our network. If you import footage with a soundtrack captured at 44.1k, the video refuses to play. Hitting play or space only results in the program monitor flickering between play and stop.
I’ve tried converting some audio to 48k and that got round the issue. Not ideal in the slightest though. Is this any help to your situation?