I am using the GroupTabPanel that is available as a UX in the examples folder in the ExtJS 4.x distribution. My page works fine in 4.0.7 but does NOT work at all in 4.1 RC2. I then tried the actual example page in the 4.1 RC2 distribution. It displays the grouped tabs on the left but the content of the pages that SHOULD appear on the right do not show at all. I checked in Firebug and all the content IS on the page, it just isn't showing. Also, it appears that nothing is happening when you click on a tab in the panel on the left. Has this example user extension been tested in 4.1? I noticed that the group tab example is NOT listed on the examples page in the 4.1 documentation.