It probably has nothing to do with the amount of RAM; I'm assuming you got the right RAM for your machine. It probably has more to do with the horizontal & vervical dimensions of your comp, plus the frame rate. AE users have coped with such things for decades, and there are a bunch of tricks to use in the viewing & previewing section of AE Help.
But here's the first trick -- never, ever use the space bar.
Well, I used it before the trip to Best Buy to get the RAM updated and it worked. Got back and it didnt. Maybe they did NOT use the right RAM for my machine?
If it's happening on projects you did BEFORE the memory upgrade, it does indeed sound like the Geek Squad stepped on it wearing golf shoes.