xserver displays only an underscore in top left corner when lightdm starts; it worked fine before upgrading from stable to testing.
if I bring down lightdm and issue startx, my desktop starts but is insensitive: mouse does not appear.
If I issue ctrl alt f2, the display still shows my desktop, but apparently it switches to a virtual term behind the scenes, because I can use
ctrl alt canc to reboot.
thanks
Fulvio Ciriaco