Ajax ControlToolKit and Firefox default button PostBack - Server Click Event

Symptoms:
Default button not does not fire when enter key is pressed using Firefox. (using the ajax ControlToolkit)
Fix:
add this property to the ASP button

UseSubmitBehavior="False"

So it looks like:
<asp:Button ID="btnSearch" UseSubmitBehavior="False" ValidationGroup="submit" runat="server" Text="Search"    CssClass="submitButton" OnClick="btnSearch_Click" />

"The problem wasn't that it didn't do a postback. That it did. What it didn't do was hit the server side event (the button click event)."