I woke up–slept in, ’cause I was up late upgrading–wandered over to the computer, and pressed the power button. It ran through the startup process into a black screen.
Luckily, escape at the grub menu, running the recovery mode, and picking xfix solved my problem. It looks like I’m not alone, so, you know. Word to the wise.
Also, Firefox 3 won’t take my del.icio.us extension, but I can use the bookmarklet.