I seem to do something like that every now and then (ergo my nickname). If I recall, I reload terminal and xfce4 from gslapt and generally it starts working again. You might have to log in to the tui to get a terminal and use slapt-get. If that didn't work, I would, again from tui, as root go to vasm and select the top option (can't remember its name). That restores some defaults.