I formatted my laptop (MacBook 2008, 1280 x 800, OS 10.5.8) and reinstalled everything. When I open AE (CS4), this is what's going on: the software behaves as the screen is a lot wider, and it looks like a decisive way to resize it and get it working is beyond my knowledge.
The FAQs I found gave no help, for they insist on grabbing the farthest sides, which is exactly what I'm prevented from, when the panels are docked.
Maximize the AE window so it fills the screen by clicking the green button in the top left, then you should be able to grab the corners of the window. If for some reason that doesn't work you can probably reset it by trashing the preferences file, but I don't think that would be necessary.