Cannot open rented movies on iPad iOS 5

I rent 6 movies on iPad 2 runnning iOS 5 today. When I want to watch them, I get the error message "cannot open". But the rented videos are working on my other iPad with iOS 4.3.I think there is an iOS5 issue with authenticating the rental time frame. Just log into a WiFi network and play the movies again. Works for me.