I have some bug with a RadioGroup and a few Radio buttons added to it. It works as expected in FF, but in IE only the first one is rendered. I was planning to write a demo to replicate the bug, but it looks like it replicates in the official GXT demo.

Please open http://www.extjs.com/examples/pages/forms/forms.html in IE 7 and you will see that for Music you get only one checkbox instead of 3 and for the Favorite Color and Favorite Fruit, no options.

Please note that I have tested and replicated it on 3 different machines with IE 7.
It seems to render fine with the 2 IE 8 machines I have tested.