Comment 13 for bug 963633

@Daniel Told, running --reset might be influenced by DISPLAY if you are using a new console (CTL-ALT-F1) so you can see what you are typing (vs CTL-ALT-T method)

My specific steps to resolve were as follows
a) Login with [username] and get *stuck* on blank screen
b) CTL-ALT-F1
c) Logged in as root user
d) #su - [username]
e) $export DISPLAY=:0.0
f) $unity --reset

Noting I could have skipped b+c if I had logged in as my normal user, and many won't have a root pw defined, this should work too
a) Login with [username] and get *stuck* on blank screen
b) CTL-ALT-F1
c) Logged in as [username]
d) $export DISPLAY=:0.0
e) $unity --reset

I have another environment not upgraded, I'll pin back so I can test the fix when it is resolved