Hey guys, very frustrated here.
I have a brand new machine running Vegas 8.0 with Core i7, 750 gb, 8gb of tri channel ram, plenty of cooling power, running Vista 64 bit with sp1.
For some reason, while working in the timeline, when I go to play and preview a video I am working on, the preview plays and then starts to "twitch" for lack of a better word. The picture jogs back and forth and progresses slowly or not at all. The audio appears unaffected and is worse on video that has fade ins/outs or any other effects.

Any ideas on why this is happening?

What kind of files are on the timeline?

.MTS files Jeff.

I think I figured out the problem, I had files on the timeline with different resolution settings which was confusing the heck on of Vegas.

I have noticed that when I switch from 8 bit to 32 floating that the picture gets jaggy in the preview window. I wonder what's causing that? It looks better with 8 bit, for some reason it seems to me that 32 should look better.

32 bit is funny that way. Just stay in 8 bit until your done editing then switch to 32 bit.