Re: Blinking Prompt After Booting
I am surprised you got that far. My GTX 550 Ti would not even get to the "Try Ubuntu" gui for 12.04 install iso on USB, just a blinking cursor indefinitely.
While booting install CD, press a key on first purple screen with symbols at the bottom and enable nomodeset kernel boot parameter. Then it should work. The installed system should work without any boot parameters.
That is sort of opposite of 11.10 where I don't think I needed nomodeset for install, but needed it on the installed system.
i5 650 3.2 GHz, 8 GB, nvidia GTX 550 Ti 32" 1080p | i7-4700, 8 GB, Intel HD 4600/nvidia GTX 765M 15.6" 1080p | etc.