As it turns out, my plumbing problem with the shower wasn't a plumbing problem after all, but an electrical one.
I've made a mental note to check on the basement heater twice a day from now on... to make sure that the breaker hasn't tripped.
*bangs head on desk*
"Life's but a walking shadow, a poor player that struts and frets his hour upon the stage and then is heard no more. It is a tale told by an idiot, full of sound and fury, signifying nothing."