Switching from SPD to SL Pedals = Knee Pain

I recently made the switch from my SPD pedals using regular cycling shoes (regular meaning non-carbon soled), to Ultegra SL pedals using carbon soled shoes. I now suffer from right knee pain that I didn't have before. This has got to be a cleat alignment issue, right? I mean, of course it feels like my feet are glued to the pedals and I may never get out (and I have checked the tension to make sure it was on the lowest, lightest setting), but I guess that's better than being all loosey-goosey with my SPD pedals. This knee pain just started with the switch of pedals and shoes. Help! Knee pain is the devil!

Very easily could be an alignment issue.

It's amazing what small little adjustments can do. I would start there.

Some people's knees apparently never do well with zero float (ability to move without unclipping). I personally like that feeling, but if you find even with correct adjustment (and a few tries with adjustment tweaking) that your knee still hurts you may have to switch pedals (seems people with very unhappy knees swear by speedplay's).