At this time I can’t add anything except that I am having the exact same problem. This is my second clean install. One thing I have not yet tried might be the problem, if you have done the same thing I did.
I installed AECS3, then I dragged copies of all my plug-ins from AE7 into the new installation. Since AE7 didn’t come with these plugins, and I didn’t install them “correctly” I am thinking this might be my problem and I will do yet another clean install, without adding a single plugin. I will share my results.