Has there been another reputation recalculation (as at 17th May 2010)?
I ask because my SO rep has dropped by approx. 15-20 points, I believe on 17th May 2010. It had been steady prior to this (I've not been very "active" for a few weeks) but I was receiving the odd up-vote from old answers. Each time my rep would go up (or down!) I could see the activity that caused this.
However, on checking my rep at some point on 17th May 2010 (in the afternoon UST) my rep has dropped approx. 15-20 points (I think) with no activity recorded that would contribute to this.