Hello together.
I experience the same trouble at the moment. After following this thread and heaving done all the tips included to hopefully solve the problem I found that changing the playback-options in the sequence-settings helped. But just in one case (a XD Cam project). Another one (DV PAL with mpeg-footage) still does not run (just sound, no picture). The code detective app found several codecs broken, but they stay broken, even if I re-install Adobe CS4 and uninstall every other video-device. Only thing I added after the last time when it worked perfectly fine are some Codecs like AVIDs DNxHD.
I work on a Dell Precision with a Matrox rt.X2 card and external RAID 5 eSATA HD.
Maybe one day there will be an answer to this issue ….
All the best,
Tobias