Black Screen After Sign-in

Ever hear of this one? This is new to me.

I log in, the little dotted circle flips a few times, and then I'm greeted with a black screen and my mouse cursor, and nothing else.

This happened a few weeks ago, but I chalked it up to a fluke. Happened tonight after two consecutive log-in attempts, the third one being the charm and signing me in as normal.

I know this cannot be good. But, I've had problems with this machine since I received it two and a half years ago. I'm ready to trash it. But... if it's an easy fix, I'd love to hear it.