Version: (using KDE 4.2.0) Installed from: Gentoo Packages A video says more than a thousand words, so I captured a video showing the problem under http://oliver-putz.com/bugreports/plasmaWidgetDraggingSecondActivity.ogv In essence, what I did: 1) Created a new activity right of the first one 2) Whenever I place widgets on the second (right) activity, I can only place widgets in the left half of that activiy. If I try to move them to the right side of that Desktop / Activity, they automatically snap back to the center position. Also note that some of the widgets keep "jumping" even in the left side of the right activity. I seem to be more or less able to reproduce this behavior. I had this problem like some minutes ago, and after I restarted KDE it went away. I played a little with plasma and there it is again. So regrettably I cannot really tell you what exactly makes it behave oddly... :-/
I can confirm this still happens on KDE 4.2.2 (Kubuntu jaunty packages). It also happens when adding more activities: every activity except the first one has this problem. If I add a big plasmoid (like a folder view) that covers the whole left side, other plasmoids will be placed behind this big plasmoid.
Here using: Qt: 4.5.0 + qt-copy-patches-942255 KDE: 4.2.70 (KDE 4.2.70 (KDE 4.3 >= 20090415)) kdelibs svn rev. 958964 / kdebase svn rev. 958965 on ArchLinux i686 - Kernel 2.6.29.1 I can't reproduce this bug
*** This bug has been marked as a duplicate of bug 181501 ***