Version: (using KDE 4.2.2) Installed from: Ubuntu Packages Pressing Ctrl while kmail displays an email message or while konqueror displays a web page shows little boxes with characters for keyboard navigation. If you scroll down while the boxes are being displayed, the khtml part (I assume) paints a track on the screen for each box being shown, because after each screen update it doens't erase the old box. The screen ends with garbage painted all over the (web) place.
*** This bug has been marked as a duplicate of bug 172870 ***