Yes, fuse #4 was blown. Working one day, broken the next...OK, I was fiddling with the headlight switch at the time, but the fuse was blown.
Rear running lights...the ones on the rear of the truck that turn on when you have the headlights on. At night with the headlights on, the rear of my truck was dark, nothing. Brake lights continued to work, but the running lights did not.