If you had a poll, for example:
[gravityform action="polls" id="6" mode="poll" cookie="1 month" show_results_link="false" display_results="false" ]
When you submit the form, it will NOT show the results as expected. However, if you return to the URL, it will show the results instead of the poll or a message that you've already taken the poll.
It only seems to happen if you have the cookie option set.