You can choose your playback resolution in premiere for smoother playback at the loss of some resolution. In the viewer window, on the top right, twirl down the menu and you will see playback resolution.
While this is not a 'fix' it can help in a pinch.
If you want true realtime playback with no quality loss, and Nvidia card is needed.
The upside is you can potentially save countless hours in realtime editing and sometimes dramatically faster encoding times.
For a list of supported nVidia CUDA cards go to the FAQ
For "some" others, with at least 1Gig of video ram, the nVidia Hack http://forums.adobe.com/thread/629557?tstart=0 - which is a simple entry in a "supported cards" file
I use the GT240, which is a low end card, and can vouch that it works great with the hack, and am very happy with it. Amazing the difference it makes in all the small things. Instant playback after color correction is huge!
Thanks guys. The info is greatly appreciated!
Ok tried to set playback resolution to 1/4 (even paused resolution to 1/4). All I could get was about 20 frames of play.... With a pro-res file. Which is not normal.... I must missing something in my settings... Any ideas?