When closing a thread to prevent responses, users are unable to vote in an open poll in that thread. I think this should be optional - as sometimes you may want a poll without a discussion, or to lock the thread whilst continuing the voting.
Thanks for the move Mike. I'm sure vBulletin does this and I absolutely hate it. I'd make a poll asking for a simple yes/no answer and people would reply with things such as "I voted yes", "Yes", "No" - how pointless.