Shoutbox

Make a backup of your Plus settings (Plus > Preferences > Save/Load > Export), uninstall Plus (and delete your settings when asked to) and uninstall any other add-on (like Messenger Discovery). Restart. If it works OK now, then delete the old Plus folder (so any leftovers are cleaned), reinstall Plus and restart. If it works OK then it was just some settings causing trouble (you can try to restore your settings), if it still fails, then there's another problem.