Grid Poll Problem

Hi...I am having a problem with grid polls.

I can create and save grid polls, but usually get the message "poll closed for voting" when I try and vote. Sometimes i can vote on a new grid poll....it seems random? (might be due to adding extra columns or options?)

Even if I have voted, the grid results table always displays 0% in every cell. The polls list correctly displays the number of votes on the grid polls.

Your help is appreciated,

Thanks...Chris.