I've tried looking into this bug and I haven't been able to have much success. Please provide a test case that implements EntryPoint, and I'll try testing it again. For reference, I'm trying it in Firefox 3.6.28 in production mode; please let me know which browser and mode you're using.
Unfortunately don't have much more atm. I'm using a SplitLayoutPanel for this and this is the only widget I could see causing problems aside from the VBoxLayoutContainer I'm using on top (I got ride of the TabPanel). I can't view anything in a VBoxLayoutContainer underneath the Split panel, regardless of whether the widget implements RequiresResize or not.
Think I'm just going to avoid VBoxLayoutContainer, it just doesn't behave as advertised in the structure I have.
Edit: Everything seems fine with a normal VerticalLayoutContainer