The problem was the starter motor was broken. One new starter motor assembly later, it starts like a champ.
Anyway, since I didn't feel like going back to work in the afternoon, (and besides, it was too late) I got a bunch of geocaches out along I-80. Traffic was pretty bad, partly because of the rush hour but mainly because people were leaving for the Memorial Day weekend. I tried I-80 first, then US-46, and then Route 10. Route 10 was busy, but traffic was at least moving faster than walking speed.