First things first:
What Os, what version, what version of AE and have you applied all the latest patchs ?
Now, what are the secs of your computer (Ram, proc, graphic card).
Are you using any opengl acceleration ? If yes/no, could you try render with/without ?
If it crashes at the end, maybe it's a file permission problem (are you admin ?) or a network problem (if working on a network).
It can also be caused by a corrupted source, so try to disable layers to see if you have different behaviors. A bad frame in a quicktime can cause such things.
Something weird just happened. After alot of rendering-tries with no success, I gave up. 30 minutes later I went to try again, and the problem was gone?
It's never happened before...
I'm on Vista SP1, After Effects CS4, don't know what patch.
Intel(R) Core(TM)2 Duo CPU E8500 @ 3.16GHz (2 CPUs), ~3.2GHz
NVIDIA GeForce 9600 GT
So in other words, problem solved, without doing anything.
Great, it's back. Fine tuned a few things and went to render again and boom! It crashed :<
Something is up with your system'r RAM and memory management. Quite clearly, once the memory is flushed after the computer goes into energy saving/ hibernation, things work again because AE has enough mmory which otehrwise is somehow unavailable. You can try the Purge option in the menu before rendering and of course the "secret prefs" (hold down Shift when accessing the pref menu), but if you ask me, this is a systemic issue and only remotely related to AE. I'd definitely checjk your device manager and BIOS for memory timing and energy management. Could even be that one of your memory bars is physically defective....