I have done a search for this - if it's still a dup my apologies.
Yesterday evening (GMT+1 this is, I'm in the UK) I went from 2833 rep to 3003 after receiving lots of upvotes on questions and answers.
I thought this was a little suspicious given the number of votes.
At the time, the only question I was directly dealing with was this question and, at the time my answer was accepted, it had one upvote. Coming back today I now find my rep has dropped to 2818, the answer is still accepted, but has now got no votes.
All the other +reps have also disappeared.
So it would seem that all votes were reversed at some point overnight and now I've taken a step back in rep!
Okay, it's only 20-30 points; but it is a bloody pain!