Dropped Frames on Playback for simple DV material - Restart Fixes it

I'm having a strange problem where RT in FCP 6 is only working after a fresh restart.

My simple test is to create a new project, new sequence (DV NTSC), drag in a small JPEG and apply the timecode generator.

After a fresh restart this plays back without issue. However, if not (ie I have quit FCP and restart it), FCP drops frames.

Any thoughts???

- T.