dynamic drop down menu got problem when got 2 pairs

Hi, I have a problem with this dynamic drop down menu, where the second drop down menu will changed when you select the first one.

When I just have one pair, it works fine but when I have 2 pairs, I got bugs. My code is in http://ilovetuition.findingsteve.net/sample.asp

When I choose State, City/Town will change. But, the first pair, Level and Subject don't work.

Thanks for any pointer for this problem.