Voting problem / bug

I have set to "3 votes" my setting to promote to the front page and allow "1 vote" per user on the same scoop, and to cast the first vote by the submitter.

This is how I notice the problem/bug:

1. Before I voted on a scoop, I opened 3 identical windows with the scoop's story.

2. Then I voted up the same scoop on all 3 windows and the scoop got promoted to the front page. (I did this with the same username)

The scoop says it has 2 votes(which is right), but it got promoted to the front page.

I tried to do the same thing at the drigg site http://designbump.com and I got a javascript alert saying I can only vote once, which means they solved the problem.

How can I solve this problem?

I'm using drupal 6.13 and the latest modules.
Here is my drigg site:
http://www.pixelelement.com/news/

I'll appreciate your help.