Sounds like you exported it at 960x540... at half-size. Do the arithmetic and you'll see what I mean. You should go back and double-check what you did, 'cause this sure doesn't sound like it's AE's fault.
It's either that, or After Effects doesn't like you. What did you do to make it angry?
Sr. Promotion Producer
KCRG-TV (ABC) Cedar Rapids, IA