When modifying the compositing settings, save a backup of kwinrc to another file to be able to revert if the X server crashes while testing the new config. Also fixed a little bug in kcmkwincompositing (dropdowns on the general tab were not updated correctly) and cleaned up the code a bit (removed a few unneeded function calls and stale connects).

See the conversation on the mailing list ("Patch for bug 174769", <a href="http://lists.kde.org/?l=kwin&m=122696916611602">http://lists.kde.org/?l=kwin&m=122696916611602</a>;) for further information.