Lock up

I am having a problem with FSX locking up on the upper task bar. As soon as I try to change any settings like aircraft, weather, or anything, as soon as I click on anything, it locks up the sim. When I use the task mgr to close the program, as the screen closes I see the screen to change the setting in back of the main screen for a split second. It worked fine until I installed FSUIPC4. I have since removed and reinstalled FSX 3 times, but it still gets locked up. If anyone has had this problem a solution would be greatly appreciated. Im running XP on a DellXPS sys with a Duo 6600 and Nvidia 8800GTX.