Ubuntu 15.04 and Ubuntu 14.04 are frozen and unuseable.

 I have my hard disk partitioned. One partition runs Ubuntu 14.04, the other 15.04. They both worked, until I executed:

sudo apt-get install nvidia-current

and rebooted.

This improved the graphics -- but neither system is now useable.

 In 15.04, I can login, and the usual icons show up on the left. But clicking on an icon does nothing. I cannot even open a terminal. (However, I did setup opensshserver for remote login on the 15.04 partition -- so I CAN execute commands remotely. ( A remote command such as thunderbird& fails, since I haven't specified where to place the graphics I don't know the appropriate way to request such a command. but,) my main conceren is: How can I fix this system? Perhaps the appropriate remote commands will accomplish this?

In the 14.04 partition, I can also login -- the usual icons do not show up on the left. If I run in recovery mode -- using an old kernel fron Ubuntu 13.1 -- the icons show up -- but, as in the 15.04 partiton, nothing happens when I click on an icon.

Help gretly appreciated,

  -- Saul