ASP.Net Error: Response is not available in this context

kalpesh helped developing the poll/voting sample: http://www.aspforums.net/Threads/203805/Poll-survey---Not-allow-the-same-person-to-vote-twice-o/?p=1. I ran into error in the Poll.aspx page "Response is not available in this context"

Response.Redirect("Login.aspx") in the Logout function.
 
Private Sub Logout(ByVal sender As Object, ByVal e As EventArgs) Handles Me.Unload
    Session.Abandon()
    Response.Redirect("Login.aspx")
End Sub

I tried to commented it out - i can see the multiple choice question on the Poll.aspx page, I selected one of the choice for example Green - it sent me back to the Login.aspx page. Do you have idea why? Thank you so much for your generous help