Regarding your suggestion about Q1, I double checked and I can find no evidence of a short between the emitter and collector pins of Q1. I replaced the transistor once before trying to debug, but I will try it again in case somehow it turns out to be the culprit. Edit: I am an idiot. I located the short between the collector and emitter of Q1, as you said I would. The story of how I am only finding it now is too embarassing to publicly relate :) Anyway, problem solved! You are the man.