Try clearing your cookies.
I did that and it looks like I can vote about every 10 minutes or so. At least the % changes after I submit.
If you open your cookies folder and just delete the one from that site and hit refresh, you can vote as fast as you can delete the cookie, refresh, and click. Not that I would do that, because it would be cheating. :)
"Reality is merely an illusion, albeit a very persistent one." ~ Albert Einstein