UpdatePanel - "Unknown Error"

I am using a drop down to fire the trigger on an update panel

This is my code:

<Triggers>
<atlas:ControlEventTrigger ControlID="DDLCountryID" EventName="TextChanged" />
</Triggers>

When I click on the drop down, I get "Unknown Error".

Your help is appreciated.

Hi,

which release of ASP.NET AJAX are you using?

In the RC, you should choose between a PostBackTrigger or an AsyncPostBackTrigger.