Thanks a lot everybody, some really great advise there. My knees have started to feel better so I started riding again today. I have adjusted my seat front to back position, increased my pedal speed and slowed myself down a bit (this was definitel the most difficult part as I am a bit of a speed freak by nature). I rode the 25 km into work this morning with no problem and I paid extra attention to proper stretching both before and after. It felt great to be cycling to work again. I'll keep everybody informed about my progress and thanks again!