Bad Running Karma or Bum Knee?

So I'm not sure what happened tonight. I started out doing the right thing by the running gods. I knew I wouldn't get a run in tomorrow because I have Back to School Night- a night despised by teachers because it makes for a never-ending day and night. I won't get home from work until 10 p.m. There's no way I can run after a day like that. So I decided to get my run on tonight, even though I was exhausted.

By the time I got to the gym (which I chose because I didn't feel up to running in the rain), it was already 6 p.m. and almost every treadmill was taken, including my favorite. So I took one of the treadmills at the front of the gym, one of the treadmills that makes it feel like everyone is staring at your bum while you run.

About 10 minutes into my run I felt a sharp pain in my knee. I knew this felt different from anything I've ever experienced, so I stopped immediately to walk. At first it was hurting to put my weight entirely on my right leg. But after a few minutes of walking, it was fine so I felt it was safe to try a slow jog. Everything was cool and there was no pain in my knee, so I sped up. (Is that what a phantom pain feels like or is it the real deal? I'm freaking out because I'm only 3 weeks away from the Baltimore Half.)

I was grooving and totally in my zone and all of a sudden the treadmill came to a screeching halt-- without me knowing it and I kind of stumbled over my feet. Apparently I had pulled the emergency stop magnet off the front of the machine. (Is it just me or is that a serious design flaw? Why would anyone put the emergency stop button, let alone a magnet right in the way of a runner's hand so it can be hit by accident?) I started running again after reseting the machine and less than 5 minutes later, I had the same problem.

I decided the running gods were trying to tell me something and that I should stop for the night before I broke my neck or hurt my knee.

Anyway, I'm a little freaked out about the knee pain, and I'm not sure what to do three weeks out. My knee isn't swollen and doesn't hurt right now. I do feel it creaking a little when I'm going up the stairs, though. Not running isn't an option. I'm determined to get a better time on this half marathon. Besides, I will go crazy without running (or I will drive those around me crazy. Either way is bad.)

Any advice or reassuring words that this utter panic is totally normal (is it?) are greatly appreciated.