i haven't a clue. never happened to me. what browser are you using? are you using tabs? etc. for example, i'm in Safari, am going to press 'Submit' and there will only post. who knows...
I don't have double post problems at home with Safari, but I've noticed it at work using IE. My solution at work is to always use the Quick Reply option - I never get a double post with that.
I get it a fair bit on chrome and using mobile web on ipod and win mob... I presumed it was because I always seem to be logged in, probably due to being logged on on another machine.
