I upgraded to KDE 4.2 yesterday (it is a big improvement; recipes are in the store), and I’ve spent a lot of today playing about with the new and old functions. In the process I managed to freeze plasma a couple of times, so the screen wasn’t responding at all except for the mouse pointer. That meant the usual way of quitting and restarting plasma wouldn’t work. It was much harder to get it to freeze this time than earlier, but just as frustrating to have to kill X and log in again (since I couldn’t run kquitapp etc with nothing responding).
However, I could log in at the console with no issue. From there I could run `urunner <<<”kquitapp plasma && plasma”` and the daemon would restart plasma for me within the session, so it had access to all the usual resources and I avoided having to Ctrl-Alt-Backspace. That was an unintended feature, but it was very handy a few times.