Yesterday I downloaded the recommended updates. I then downloaded Minecraft, which meant downloading a Java package and changing a Nvidia setting. As per instructions I performed a shutdown/startup on my Dell Inspiron. It initially opened and I was able to play Minecraft. However, after shutting down have been unable to boot the laptop since. I get a back lit black screen followed by the purple screen, more black with flashing cursor and then the Ubuntu start screen. Then a whole load of commands rush past and we end on a black screen proper. And there we sit. I know something is happening in the background as fans are operating. No matter what configuration of keys I press during the abortive start up, I cannot access the terminal to attempt a repair. I have seen many with questions but no definitive answer. So, I'm seriously tinkering with the idea of just saying bollocks to it all and doing a clean install. Before I lose all data and settings, has anyone got any good news and doesn't require a PhD in IT to execute. Hope everyone is having a better day than me. Cheers.
If this is solely about good news, since this is Ubuntu we're talking about a clean install while keeping all your files is possible (though I would still recommend backing up your data before a clean install).
To do this, boot up the computer using an Ubuntu Live CD (or USB) but don't install anything. Instead open up the folder manager and your partition where your home directory is should be there.
If your home directory is encrypted here's how you do it: http://www.howtogeek.com/116297/how-to-recover-an-encrypted-home-directory-on-ubuntu/
Solved, but kudos to Thanos and Joe.
Not the ideal solution, as I will have to set everything up again and backup data from ext HD. However, it did fix the problem.
Firstly, I performed a clean install of Ubuntu, effectively wiping the HD. Next I went back to the original help file at 'How to geek'. This time, however, I did not mess with the driver settings for the NVIDIA. I did download 'openjkd'. After that I just downloaded the Minecraft.jar, following the 'How to geek' guide.
Opened Minecraft and played for minute before closing and shutting down. On start up everything booted without a problem.
I can only conclude that changing driver settings caused the black screen issue.