"Callback Error: Invalid response from server" from C# ASP.Net application
<p>I have an ASP.Net application with a button containing the following Javascript to be invoked when it is clicked:-</p>

<pre><code>    function calculate() {
        sectionIndex     = getSelectedRadioIndex("section");
        compositionIndex = getSelectedRadioIndex("composition");
        CallBackOU.callback( "calculate"   , sectionIndex, compositionIndex );
    }
</code></pre>

<p>I can verify that control reaches the last line of this function by setting a breakpoint on it. But instead of invoking the method in the code-behind file...</p>

<pre><code>protected void CallBackOU_Callback (object sender, ComponentArt.Web.UI.CallBackEventArgs e)
{
    //blah blah
}
</code></pre>

<p>I get a dialogue reporting </p>

<blockquote>
  <p>Callback Error: Invalid response from server.</p>
</blockquote>

<p>This dialogue appears three times, after which the page sits there doing nothing (forever, so far as I can make out).</p>

<p>I can't find any information about this. Can anyone give me any clues or pointers about how to go about diagnosing the problem?</p>
