I still have no idea how it works (or doesn't work) but I found this on their page:
From their page:
In order to vote you need to provide a valid email address, and only one vote per email address is possible. If after voting the first time, you decide to vote for another image, the first image you voted for will lose that vote.So I went and registered. Still Henry's pic was on 5 votes and told me "thanks for voting". But: I then was able to change my vote to another pic, and Henry's count went down to 4 votes. Then I voted for Henry's pic, and it was back to 5 votes.
I still don't understand how it exactly works, but it may be that if you click the permalink, it counts your vote automatically and at the same time registers your IP.
I put the permalink here, would someone please click on it and tell us if Henry's count gets up to 6 when they clicked it?
http://www.worldinfocuscontest.com/bin/Rate?image_id=1006800299