Version: (using KDE 4.0.83) Installed from: Ubuntu Packages When I add a new widget on the desktop, instead of drawing the widget it just shows a featureless gray circle in the upper left corner of the screen. Widgets that worked perfectly in KDE 4.1 beta 1 (like Comic Reader) have become useless. Most widgets in the menu behave that way now. A few, like the "New Devices" and the "Trashcan", work well as before. When I add these faulty widgets to the panel, it just adds a black space at the far right end with the name "Unknown Applet".
Maybe you're trying to add plasmoids from extragears which couldn't have been yet updated on the ubuntu packages. Did you updated ALL KDE4 packages?
same problem occured to me with the openSUSE packages (KDE:/KDE4:/Factory) (extragear if I remember correctly). Personally I think this is/could be a packaging problem.
*** Bug 165113 has been marked as a duplicate of this bug. ***
FiNeX: Yes, I updated the system this morning. Actually, I deleted plasma-extragears and re-installed it from scratch to make sure the packages were not corrupted etc, but the result is the same.
The applets that don't work are from the extragear-plasma package. It is an old package (his version number is 4.0.80). Upgrading to the new package (renamed kdeplasmoids, version number 4.0.83) solves the problem.
Albert: It does indeed. The applets work perfectly now. Thank you!
Closing as it's solved!