failed online update 12.10 to 13.04 black screen

[Uriah Heep]

I have a basic Lenovo G580 laptop with and Intel I5 running at 2.5 GHz and
except for adding a second four gig stick of memory I have not modified
it.  Video is handled by the I5.  Of course, Windows 8 was installed though
I would rather not have to pay for it.  I installed Kubuntu 12.10 in a dual
boot configuration and have been using it for three months without issue.
I then did an online upgrade to Kubuntu 13.04.  I rebooted the password
screen came up, I entered my password hit enter, and now have a black
screen with the exception of the mouse cursor.  When experimenting hitting
the print screen button brought up the screen capture program.  From there
I was able to get into Firefox on exiting Firefox I was again confronted
with a black screen.  After invoking screen copy again, I was able to get
printscreen to show other areas such as root, grub, etc.

Would anyone be able to suggest a way I could get my regular home screen
back?
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