I've had a problem with a pretty serious lag when playing back from the timeline in premiere CS5. The UI is responsive, but the playback won't start before 5 to 10 seconds after hitting play. This happens to me while editing SD .mxf files and DNxHD 1080 quicktime files. I've not been able to test it more extensively yet, but the symptoms have been similar on to different hardware setup;
#1: HP xw8600 - win 7 64 bit, CS5, 16Gb RAM, Nvidia Quadro FX 4600, 2 X Xeon 5450, 2 X 300 Gb SAS HD's, one for OS, one for media.
#2: HP z800 - win 7 64 bit, CS5, 24Gb RAM, Nvidia Quadro 6000, 2 X Xeon X5660, 1 X 150 Gb SAS for OS, 2 X 300Gb striped SAS raid for media.
Latest updates and drivers all over.
I realize that DNxHD might not be optimal since it's an old, outdated format, so any suggestions on what to render from AFX to get HD-playback on the timeline in Premiere is very welcome. I installed mainconcept codec suite trial which helped mxf playback, but messed up the sound channels (i only get 1 mono channel from the source files originally there's two).
Any suggestions are welcome!