I hit the rep cap today, and then downvoted a question. Somebody upvoted one of my answers, so I was back at the cap again. Then I removed my downvote - I'm still left with that +1 I got in the meantime. I triggered a recalc, but it didn't change. Something there doesn't seem right to me.
Edit: My total rep seems to have just gone down by one, but the reputation page and the summary I get by clicking my name at the top bar are still showing this extra one.