This morning I heard back from a potential committee member, and he graciously agreed to serve on my committee with a proposal defense date before the end of January. At last, I have a full committee again and I am back on track to take my comps before the start of the spring semester.
Of course, the down side is that I have to hit the books hard and make sure I can pass the exam, as well as put together a brief for my proposal defense. I guess every silver lining has its cloud. But I am grateful I have found a fourth committee member at such a late date.