I went in and whined at the cashiers. They called a guy with a truck, who came over and had a look. Long story short, I needed a new battery, which we got from O'Reilly Auto Parts, and after an hour or so, I was finally able to leave Vicksburg!
So I drove across northern Louisiana, stopping for lunch in Monroe, and finally reached Marshall, Texas, where I had to say goodbye to the interstate and take US-59 home. US-59 is a useful road, but it annoys me with its non-interstate-y-ness. Instead of letting me just go straight to Houston, it wastes my time screwing around with traffic lights in small towns.
Aaanyway I finally reached Houston, had dinner at China Stix, and came home. Whew! Tired now.