Is the current-time indicator at the end of the composition or work area and you have From Current Time selected in the Preview panel? This error comes up under some other circumstances, too, but it's best to eliminate this simple one first.
BTW, you can search for the text of the error message using the
After Effects Community Help search. This brings up several threads talking about this message and some possible causes.
It's your memory allocation most likely. If this error creeps up with MP, it usually means there is not even enough RAM for all the source footages to be loaded, let alone render out something... What's your hardware?