Without knowing anything about your compositions or the effects used I would suggest that you turn off MP rendering. It's buggy and sensitive to codecs, effects, and temporal changes. See if that helps.
Rick, please read my third paragraph. While yes - disabling multi-processing helps, effectively turning my computer into a one-processor machine instead of an 8-processor machine is not a solution.
And I experience these long delays even with NO filters or 3rd party effects whatsoever. I just rendered an animation that was nothing more than a couple sliding illustrator layers with a 3D camera move and the render took 3 full minutes to get beyond "initializing background processes, this may take some time...". This just after a fresh launch of Adobe After Effects.
Did you ever solve this problem. I am in exactly the same situation and everything is getting worse and worse. aeselflink going crazy by not responding i activity monitor and i can't render at all some times.
Any help on the subject would be much appreciated.