When you refresh the page, do you get the prompt to post the data again? If so, you are probably clicking Retry instead of cancel and therefore the data is posted again and again.

Hope this helps.

I have experienced the same thing a couple of times in the past few days.

I created a post, had a buddy of my comment on the post, and he was waiting for me to post a response via comment to his comment.  So he kept hitting refresh, and it re-posted his original comment each time he hit refresh (and he did not get prompted to re-submit the data to the server).

Thanks,
Brian Swanson
http://blogs.purpleant.us/bswanson