Can't log in or get to Recovery mode after update

I should prefix this by saying I'm not a Linux expert so please bear with me!

Have been running Ubuntu 10.04 with no issues on my toshiba laptop.

After the latest update last week I can no longer log in.

If I allow the laptop to go through the full start up process it shows the normal purple screen but "Ubuntu" is in courier script rather than the normal large image (is this the low graphics version?) and when it goes to the login box I'm unable to type in my login or do anything - can't use the keyboard or mouse it's just frozen.

Tried to go through recovery mode but I can't get further than the choice of recovery modes - the system runs through it's cycle but doesn't appear to finish - I get a flashing cursor but can't enter anything. I don't get the grey/green screen bit.

Whichever option I try I end up stuck, can't get to a terminal screen, login or recovery mode. Tried Memtest for the hell of it but it says there's no errors.