Short story: qt-4.8.4 on Fedora 16 might offer you crashes when clicking the menu in the panel. I had this on my main user account, but not another account. Downgrading to 4.8.3 solved this with the exact same .kde, .local et al in place.
The crashes offered my g_iterator type things in the backtrace. Nothing juicy that I could try to work backward from. Digging around seemed to show theme stuff, pointing at the nvidia drivers (which always comes up in searches), and there was a bug I found along the way mentioning qt 4.8.4, so I reverted to 4.8.3 from a mirror that had the old packages still around.
I decided to update the laptop before a trip on thursday, and this was of course when I discovered this little bundle of joy. I'm not sure which part of my config was causing this, but at least I can now use the laptop with my desktop of choice while away!