Version:           Unbekannt (using 4.2.4 (KDE 4.2.4), Kubuntu packages)
Compiler:          cc
OS:                Linux (i686) release 2.6.28-13-generic

I don't know how I triggerd this, but since my change from Ubuntu to Kubuntu (just installed the packages) my plasma Desktop is weird:

I can add any plasma widget to the desktop, but it does not keep it's position. Maybe two seconds after created or moved somewhere, the widget "jumps" to the upper left side of the screen.
It's not always position "0,0", e.g. if there already is the "Folder View" plasmoid, the second one somehow arranges itself right next to the Folder View.
If I move it to the right, it stays there for 1-2 seconds and then returns to the left.

This makes plasma unusable.
I can not reproduce the bug with a fresh user, but since it's the second time I have this problem after working a while with KDE, maybe I can provide you with some of my config files If you tell me which ones are the relevant?