Another failure

[Ted]

I have just reinstalled Ubuntu as the last install was ok for a couple
of weeks the it refused to let me login...
  I reinstalled a couple of days ago and all was well...
I just went to the box this morning and found Icould not write an 
address in Firefox so I went to a terminal to remove and reinstall 
Firefox and found I cannot write in a terminal so cannot email or use apt...
Any advice welcome as I do not want to ditch Unbuntu.

-- 
Regards
  Ted Wager
   Linux user