Strange Object Reference Not set to instance of an object

 Guys I am in Big trouble.. if any one can help me it would be a favor
I have written a code
 
protected void BtnAddNew_Click(object sender, EventArgs e)
{
try
{

//SOME PIECE OF CODE
}

catch (Exception ObjException)
{
LblMessage.Text = Resources.messages.ExceptionMessage;
new HandelError().ManageError(ObjException.ToString(), Request.Url.ToString());
}
}  In My system it does not throw error but on my client PC its throwing error of NullReference error... And intrestingly that error is coming in Yellow screen... How ever I have packed the code from Head to toe in try block
 
The site is hosted on the same server... we are accessing the same site...
Here is the stack trace which co ...