Comment 12 for bug 336320

Anyway, about your bug... We have a potential jaunty fix for another bug, namely #368049 in the pipeline and that stacktrace looks similar (but not identical!!) to your stacktrace. However, due to the nature of this bug I suspect that the fix for #368049 might possibly fix your issues as well. We cannot be sure so we need your help. It would be _very_ useful if you installed this update and saw if it fixes your issue. And while you're at it, please test for regressions as well!

From a machine with Jaunty, what you need to do is; to open System::Administration::Software sources and then switch to the "Updates" TAB. In there you need to check the "Pre-released updates" checkbox. After that you launch update-manager like usual and you'll a bunch of untested updates available. Ideally you should not install all of them blindly (but it's not a disaster if you do I guess, it's just that we can tell for sure if a potential regression came for the mesa update), instead you should:

Select all the updates where the package name contains the word "mesa", for example libgl1-mesa-dri and libgl1-mesa-glx are the two most important ones but please install all of the mesa updates, even libosmesa, mesa-utils and libglu1-mesa etc. After that just reboot the machine, and then try running the "shift switcher in cover mode" as you described earlier.

If this does not fix your issue, the next step would be to get this bug report upstreamed. But let's wait and see...