Do not use MUON to upgrade your system the first time!
Right after Installation, please update from KDE 4.9.4 to 4.10.2:
Start Menu – System – Synaptic Package Manager, click “Reload”, then “Mark all Updates”, then “Apply”!
At the error message about Muon, just close the message window and click “Apply” in Synaptic again, which should fix Muon and update it to 2.0!
sudo apt-get update, then sudo apt-get dist-upgrade also works fine!
Otherwise Muon may break with the latest Kubuntu 4.10.x packages, so it is advised to do the initial update right after installation. Muon will then update itself to 2.0, so after that Muon should work fine again, so you have a fully updated system with latest KDE and Muon 2.0.