Did you re-boot? Did you try re-booting in safe mode? Did you add anything to your computer or run any updates between the first render and the time this problem started?
Did you try creating a new comp, adding a single solid, and then rendering? If that works tell us about your source files including type and compression.
If that fails then make sure that you have run all the updates. Then, make sure you have not installed any 3rd party codec packs. Then, dig up the error log and look for anything you can find that starts with "unable" or "crash" and that may give you a hint.
Yes I rebooted the computer, No I didn't try it in safe mode. I didn't update anything or add anything between the renders.
I did try to render with just a single solid and it worked.
Not sure about how you find the 3rd party codec packs or the error log, can you give me some guidlines on how to find these? Still kind of new to After Effects (been working in it for a year or so)