frequent error

Recently there is frequent error with the plugin which i have come across. After activating the poll it look fine for a day but in the next day when the poll page are open. It shows that all the poll show “Already voted” thou we try in different system or ip address. in order to solved the problem we have deactivate all the poll and the activate it again then it will be fine for or a day sometime for hour only. So this problem are face everyday and the admin has to do the same process said above every day in order to run the poll. I think is some error with the plugin and hope it got fixed by the developer. Thanks the plugin is awesome last year i have used the plugin without any issue but this time i don’t know whats wrong?

The page I need help with: [log in to see the link]