I was working on my mini movie and I was rendering as I went along. I saved it and came back to it to add more but now it won't render the stuff I did before. I clicked render effects, nothing, I clicked render entire area nothing.
Edit: I'll be a bit more specific, in that there are bits that aren't green, they are yellow. It lags slightly with the yellow bits but everything else plays properly.
Go to Sequence>Render In to Out.