I have encountered this bug as well, and it seems only to affect non-KDE applications. Reproducing the problem:
Right click on the panel to bring up the context menu. Select Add->Application Button->Debian->Apps->Net->Gaim (any non-KDE application will have the same problem) Right click on the newly-created button to bring up its context menu and select Properties. Click the icon, select a new one and click OK The error message will be "Could not save properties. You do not have sufficient access to write to /var/lib/menu-xdg/applications/menu-xdg/gaim.desktop" Other symptoms: chmod a+w /var/lib/menu-xdg/applications/menu-xdg/*.desktop fixes the problem temporarily, but the permissions are usually reset after an apt-get update && apt-get upgrade and the problem reappears. Platform: Debian Unstable i386 (updated August 7, 2004) Kernel 2.6.7-1-k7 libc6 2.3.2.ds1-15 kicker 3.2.3-1