There is a typo on the description field of the Poll.
to fix:
edit /portal_skins/custom/PlonePopoll_view2
change word must to most
changed choices to choice(s)
:-
You can vote at most for <span i18n:name="number"
tal:replace="number">#</span> choice(s) on the poll. If
you vote again, your old vote is replaced by the new vote.