Ubuntu support question: massive GUI failure. Reboot is not helping.

I recently wired my computer into the television (my graphics card supports such shenanigans). Windows is fine running two separate monitors, and Ubuntu supposedly is, as well.
I rebooted so that the new settings could take effect, but to my surprise and dismay, the GUI failed to load. I am still enough of a novice that I’m next to wholly useless with the text-based interface, and so I was wondering if you could help me bring the other one back up.
It’s a recent installation; I’m not worried about losing any data.