With kdebase 3.1-0.2 I am getting the following errors, which prevent the desktop entries from showing up in the menus. # kcmshell desktop QMutex::unlock: unlock from different thread than locker was locked by 0, unlock attempt from 8192 # kcmshell panel_behaviour QMutex::unlock: unlock from different thread than locker was locked by 0, unlock attempt from 8192 same for kcmshell panel and perhaps others.
It's fixed in 3.1-0.9 or newer.