UAG Login.asp customization error

Hi,

I am trying to customize the Login.asp for a trunk configured with 2 authentication servers. I am having a checkbox and wanting to select the repository based on the checkbox value. I am successful with having a checkbox and setting the value in the textbox with ID repository. I am also able to access the login page. But, I am getting the below error when I hit the 'Log on' button:

Please help me resolve this issue and move forward.