Software update won't work?

When Apple released the 10.6.5 beta for AirPrint testing, I installed it, thinking nothing of it. However, I have realized since then, my computer doesn't recognize software updates (major ones) such as today's update to 10.6.6. Nothing comes up, as if it doesn't realize a new operating version is out... Can anyone help me with this? Kinda bummed out about no being able to update anymore.

P.S. I also noticed this happened with the iTunes 10 beta, now when an iTunes update comes up, it does the same as decried above, doesn't exist according to my computer.