I'm not sure but maybe these sites will help you out.
http://www.katsbits.com/htm/tutorials/blender_ao_baking_terrain.htm
http://www.blender.org/development/release-logs/blender-243/render-baking/
http://blenderartists.org/forum/showthread.php?t=148610
Some quick things to check though:
Do you have a light in the scene? If not, is there a global light than is being used? If you are, is it close to your model so it's being lit?
Are you outputting the AO Map render onto your texture automatically?
"If I have seen a little further it is by standing on the shoulders of Giants" - Isaac Newton
-Computer Animation Major @Baker.edu-
