Question about knee issues

When I decided to start running (C25K), my hip decided to act up. I took a break from running and started walking on the treadmill and my hip is now fine.

However, after my workout today I noticed the area just above the back of my knee is hurting. Not a sharp pain, just a dull achy type of mess. I'm not entirely sure what it is or how to find out what it is. I am not sure what caused it, either.

I am doing 60 min on the treadmill on the random elevation setting. I've been doing 3.4 mph but today I bumped it up to 3.5mph.

Anyone have any suggestions on what this is and how I can stop it. I plan on resting it, but again, I'm not exactly sure what "it" is. :)

Take this for what it is - a possible cause from some dope who has had some knee problems and done some research.

It sounds like it may be from a tight IT band which is the muscle that runs from the hip to the knee.  When it is tight it can pull from the knee and cause pain. 

Here is the best site I have found for stretches for it.

http://www.rice.edu/~jenky/sports/itband.html

Thanks Scott. I'll try those stretches and see what happens. :)