Had a weird problem yesterday when I tried to update my system through the Muon Package Manager. It tried to install a bunch of kde 4.8 updates and ended up uninstalling plasma-desktop. As near as I could figure out the problem was unmet dependencies and was fixed by enabling the kubuntu backports ppa and running a dist-upgrade. Not sure what is going on here, but I wanted to share the problem and solution in case anyone else runs into a similar problem.

Also, if you have plasma-widget-icon-tasks installed from the gnumdk ppa it will break the update to KDE 4.8. Bug report and solution to the problem can be found here, https://bugs.launchpad.net/kubuntu-ppa/+bug/913080