Someone just posted this same issue on another thread. He said he did a hard reset (Hold power and home button) while his phone was plugged into his computer. He said it started right up after that.
Yes, if you'll see, this worked for me too. It's very odd. This had better not happen every time the phone needs to be restarted, or I'm going to need to go back to stock. I can't do the whole untethered jailbreak thing.