After reading the symtoms I think I may have this also. I find I can bike quite a bit but not run at all and sometimes just walking can cause the pain. I had to mess around with my seat height alot to get around this. this may be all in my head but who knows.
When biking focus on the angles of your knees if you can try to put them mechanically proper. Not sure if that makes sense.
I tend to agree with what someone said about 3 times to run. Personally I find it far to high impact to be usefull there is many other less impacting cardio activities you can do other than running. I have always been a huge fan of biking or even punching a bag for some time.