the Y axis was inverted starting with CS5, check this page. Look at the comments for a way to put it back the way it was.
Thank you very much. If I understand correctly, your solution gives me the option to change back to the CS4 and previous coordinate system, based on the 1st quadrant, as opposed to the 4th quadrant used in CS5 and 6.
I didn't get it either, and many people complained about the switch, apparently they wanted to make all apps the same, I guess, I don't remember what the excuse was...but yeah, you can change it back and forth to your taste.