Seems to be a lot of threads starting everyday that are having problems with jQuery UI 1.7.2 and jQuery 1.4.x.

I'd like to try to help by putting this information more up front.

jQuery UI 1.7.2 is only supported with jQuery 1.3.2

and 

jQuery UI 1.8 RC 2+ is supported with jQuery 1.3.2 and jQuery 1.4.2

You need to use the right version of jQuery with the right version of jQuery UI.

If you run into problems with jQuery UI please make sure you are using the correct version of jQuery for the version of UI you are using.

jQuery UI 1.7.3 will be released after jQuery UI 1.8, to make the 1.7 plugins work with jQuery 1.4.2.

Hope this helps!