I have exactly the same problem at the moment. The files are video footage of a Canon 7D, that i mixed together. Rendering also stopped halfway with that message, so i changed the saving destination to my internal memory. This is CS6 AE. It does rendeer completely after changing the mem save, but when i try playback it isnt smooth and it doesnt freezes during the duration. Please help me!!! Im not sure what settings to edit.