If I kill the panel without exiting properly, say with SIGINT, I get a bunch of dialog boxes telling me about each of my external plugins unexpectedly being removed, and then after closing those dialogs, the panel quits. When I restart the panel, all of the external plugins are now missing. I'd suggest not removing the plugin from the config if it quits unexpectedly. This may be due to a transient problem that the user can fix. IMHO gnome-panel handles this the right way: it says something like "There was an error starting [applet name]. Do you wish to remove it from the panel?", with a yes/no option.
Agreed. I'll have a look at it.
Btw, this doesn't seem to happen to me. The panel aborts abnormally on my system fairly regularly, as you may understand ;-) On abnormal termination the panel should not save its settings. I don't think it does, but I'll have a closer look. (At some indefinite time in the future ;-)
Not sure if this still happens (can't test right now anyway), but here's how it did it for me: 1. Start xfce4-panel from a terminal window. 2. Hit ctrl+c in terminal window. 3. Panel pops up a dialog for each external plugin saying it terminated abnormally. 4. Close each dialog, then panel quits. 5. Start panel, all external plugins are missing now.
Seems to be working OK now. I don't get dialog boxes anymore, just glib CRITICAL messages to console, and the plugins are properly restored when I start the panel again.