This came up in Raymond Camden's CFUnited presentation this morning and he suggested I blog it so here it is.
You have extended the cfajax tags by calling the extJS functionality directly. CF8 uses extJS 1.1 whereas CF9 is going to use extJS 3.0. There will be cases it appears where this will break your code as some features have changed from the 1.1 to 3.0 release.
(Edit 10/14: I made a minor change to item 1 for clarification)