Version: (using KDE 4.1.2) OS: Linux Installed from: Ubuntu Packages I do use the combination of the keyboard switch applet with the kmix applet. And it appears that the background of the kmix applet looks like the swiss flag which is one of the keyboard layout used. I've put an image of it on: http://obswww.unige.ch/~briner/bug_kmix.png
I can confirm that Kmix in 4.1.2 often gets garbage in it's background, as in your image.
However, I don't think this bug is specific to Kmix. I started the KDE4 version of Klipper and it seems to have the same problem. So I think it's a generic KDE4 problem - or maybe even a bug in QT. Can you confirm that all your other system tray icons are from KDE3? (look in Help->About, or version information in your package manager). I have a KDE3 knetworkmanager icon, and that's not affected. I'm guessing your battery monitor is KDE4, but it's a plasmoid and not a system tray icon. (If I'm right, you can move the battery monitor icon around on the panel independently, whereas the system tray icons move as a group).
This looks like a duplicate of the long-standing Bug #158094. Please mark it as such (and close it). The last comments on that bug claim there is a workaround, and that it will be committed for KDE 4.2.
As explained in comment 3, this looks like a dup. *** This bug has been marked as a duplicate of bug 158094 ***