Early on in the relationship, my wife had some serious trust issues. Broken home and a sibling who was a compulsive liar did a number on her. We were in the car once and the following conversation transpired as we were returning from an afternoon matinee:

ME: "So when I was talking with Bob earlier, I...."

HER: "I thought you said you didn't talk to Bob today."

ME: "Uh, no, I don't recall saying that, because he called me earlier. Anyway, I was telling Bob that...."

HER: "No, I'm pretty sure you specifically said you hadn't spoken with him."

ME: "Okay, sure. Whatever you say. Not important. ANYWAY, Bob said...."

HER: "I mean, why would you lie about that? Why would you not want me knowing you talked to Bob? I don't understand. Why would you LIE?"

ME: "Look, I don't recall this conversation, but it doesn't matter, does it? He called, we talked, nothing important. Can I carry on with my pointless story?"

HER: Dead silence for the rest of the drive because she thinks there is some nefarious reason as to why I was lying earlier about speaking to my friend Bob who had never even come close to being a point of contention

I'm willing to bet she either doesn't recall this event or would probably just chalk it up to being moody, but I remember it totally ruining the vibe for the rest of the evening.