Error Object reference not set to an instance of an object

I am getting the error below viewable at this link:  http://ibahnsurvey.com/Default.aspx?macaddress=12345&sitecode=ibahn

if you do not get the error at first, wait 20 seconds and continue filling the form out and eventually you get it.  

Any ideas what is wrong?

Server Error in '/' Application.
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Object reference not set to an instance of an object. 
Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code. 
 
Exception Details: System.NullReferenceException: Object reference not set to an instance of an object.
 
Source Error: 
 
An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below.  
 
Stack Trace: 
 
 
[NullReferenceException: Object reference not set to an instance of an object.]
   GuestSatisfactionSurvey._Default.Page_Load(Object sender, EventArgs e) in C:\applications\GSS\GuestSatisfactionSurvey\GuestSatisfactionSurvey\Default.aspx.cs:24
   System.Web.Util.CalliHelper.EventArgFunctionCaller(IntPtr fp, Object o, Object t, EventArgs e) +14
   System.Web.Util.CalliEventHandlerDelegateProxy.Callback(Object sender, EventArgs e) +35
   System.Web.UI.Control.OnLoad(EventArgs e) +99
   System.Web.UI.Control.LoadRecursive() +50
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +627
 
 
 
 
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Version Information: Microsoft .NET Framework Version:2.0.50727.3053; ASP.NET Version:2.0.50727.3053

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