I'm working on an SD video project and it's getting really annoying because every time I press Play on the Timeline I have to wait while Premiere renders the files. I do mean every time as well. This is even when I have already rendered any previews.
I have CS6. 10GB Ram, separate HDDs for system, footage and preview files. Windows 7 64 Bit, 13 3.30GHZ CPU ATI Radeon 512MB card.
I've seen this happen on occasion where PP get's confused about things.
Maybe try creating a new sequence, then Copy/Paste everything into it. See if that new sequence behaves any better.