I'm glad the OP is alright. I always travel with pepper spray, knife, and a bright holster mounted Scorpion or Surefire flashlight. Hearing about the OP's chain problems frighten me. I'm glad I commute on my fixed gear, but chain problems can affect those as well. My friend and I do a lot of our riding at night in down town. We always come across people on the streets at night, either waiting for the bus or just hanging out. The first option is always to haul out of there, running as many lights as we can. It sucks to think of everyone as a potential assailant, but whatever it takes to get me home. I tried listening to a radio with one earbud when I first started commuting, but it just made me feel so disconnected from my surroundings that I stopped before a another block passed. I'm more concerned with drivers than I am muggers, though. You can usually see the footmounted miscreants, it's the caged ones that can cause some big problems. Again, glad you're safe.