I have four desktops on Mint KDE Isadora. When I try to right click on any desktop other than #1 Plasma seems to crash. The task-bar disappears, widgets gone, etc. I can still switch desktops from Cairo-dock or by mousing to the edge of the screen though. Previously, I had different settings on each desktop. I have all the latest updates. I am a Linux noob so I'm not really sure even where to look to start troubleshooting this problem. Additionally, a problem that may be related that I'm having is that I cannot logout/restart/shutdown/switch user from Kickoff, Lancelot, or Cairo-dock... but only from one user account. The other user account seems to behave normally.
Linux IcyMint 2.6.32-23-generic #37-Ubuntu SMP Fri Jun 11 08:03:28 UTC 2010 x86_64 GNU/Linux