Just a suggestion, why not set up the voting so that rather than only being able to vote every 12 hours, it has 12 hour periods where you can vote?
For instance, with the current system someone who votes at 6:25:44am would have to return at exactly that SAME time 6:25:44pm 12 hours later to vote again.
However, if it were to work as per my suggestion, let's choose 12am and 12pm server time for the "reset" points. Someone who votes at 6:25am, could vote again at 3:50pm if they so desired, and then again at 12:01am, and so on and so forth, perhaps this system is due to something with the actual vote site, but if that's the case we could just shoot them this suggestion and see if they go for it, if not, I'm perfectly fine with being late for work because I want a crazy new hat.