My laptop is dual-booted with Windows 8 on one partition and Ubuntu 12.04.3 on the other. I've searched for my issue already, but nothing I've found so far has solved the problem.

Since last week, when I try to boot Ubuntu from GRUB, I am taken to a purple screen (as usual), but then to a black screen with a blinking white _ cursor. I've tried leaving it, but nothing else happens. When I hold Shift and edit the GRUB entry to change 'quiet slash' to 'text', the back screen instead asks for my login and password. When I put them in, it tells me the date of my last logon, and then waits for further commands. Being very very new to Ubuntu, I have no idea at all what to try out at this point.

I tried to launch FailsafeX, but while that was beginning, it said "unable to run server /usr/bin/x" No such file or directory", then shortly after returned to the recovery mode menu.

Pressing Ctrl+Alt+Delete goes through an Ubuntu loading screen, then the laptop then restarts.

Any suggestions will be very appreciated, and apologies if this is a common issue that has been answered a million times before.