Excellent advice Bern and another great example of why "fit" can make a difference. We can get by with being out of position until we really start to pick things up.
I had exactly the same experience and now ride with the cleat on my right shoe a little more forward than my left. I got the knee pain in the same spot as you after doing some pretty hard and long climbs.
You can't suck at climbing any more than I do.......although like you I'm getting a little better at it.