I'm having problems with dolphin when I sudo dolphin, or use root privileges opening it, and then logging out will hang your computer and would have to reboot. :( A workaround to this is using Nautilus as your file manager in KDE 4.
1.Install Nautilus using Synaptic, or System Settings->Add and Remove Software.
2.System Settings->Default Applications->File Manager and choose Open Folder, then Apply.
I also found out that this fixes the bug in Quick Access widget in Plasma on the panel.