asp.net - Issues with User Control inside repeater -

i using asp.net have created user control this: when pressing + : score raised 0.5 , opposite minus.

the user control contains update panel, , pages containing script manager.
when put user control in page , not inside repeater, works perfect. when put part of repeater. not work @ all. tried delete update panels , still not working.

this error i'm getting

don't know how fix this. code of user control:

often, error shows due not post back:

if(!ispostback){      // controls code here  } 

or, check web page not using <form> tag more once:

<form id="form1" runat="server">     <form id="form2" runat="server">         <!-- user controls -->     </form> </form> 

you have use 1 <form> tag in page.

or, try in *.aspx page like:

enableeventvalidation="false"