Yes, LabRat, You're right. That's the scene I'm talking about. It's the scene just before the last scene in the episode "Faster than a speeding Vixen" (4.17).
Clark and Lois are in bed, kissing. Then Clark stop Lois and said "what about protection, honey ? You want me to..." and Lois turn towards the nighstand and said "no, no, I got it", while Clark turn off the lights.
