bunglehead, as you've already probably decided, it may be IT band friction syndrome, which is a knee problem that develops when you overtrain to quickly in running or hiking (like when you go out on 15 mile canyoneering day trips after sitting on your ass for a month, which is what happened to me a few years ago).
Does the pain begin as a barely perceptible warmth on the outside of the knee, and steadily grow until it's unbearable? Then it's probably IT band friction syndrome.
When I had it I did the stretches that are prescribed for it before, during and after exercise, I cut down on long hiking approaches for the entire summer (a bummer I know but the pain fucking sucked on the hike out), and I started riding my bike alot more. All three things helped and three years later I still don't have any problems with my IT Band.
Good luck