When upgraded to wordpress 3.1.1 this plug-in stopped working for me. Upgrading to 3.1.2 did not resolve the issue.
I am able to add, and setup a new poll with out any issue. However, when trying to vote the screen shows "Loading" and does not ever refresh to the results view. The vote isn't being stored either as I can look at the logs for the poll and see no update.
I have read other accounts of the wp_head() and wp_footer() required in my theme for this poll to work. I have looked at my theme's files and both these are present.