AJAX/ATLAS: Errors after you click the browsers back button

[Darren.Ratcliffe]

Hi everyone

I am getting the above problem when I am trying to use AJAX on my
Visual Studio 2005 solution - I seem to keep getting it when I click
the back button in my browser. (And, the controls that are wired to
the AJAX lose their value despite being in the ViewState).

I am using the latest version that I downloaded from ajax.asp.net a
couple of days ago.

What I have is four heirarchical drop-down boxes in an UpdatePanel, and
when you change the first box it changes the second, which changes the
third... you get the idea I am sure :)

Any help would be very much appreciated.

Many thanks in advance for your help

Darren

Full error message:

Invalid postback or callback argument. Event validation is enabled
using <pages enableEventVali dation="true"/in configuration or <%@
Page EnableEventVali dation="true" %in a page. For security purposes,
this feature verifies that arguments to postback or callback events
originate from the server control that originally rendered them. If
the data is valid and expected, use the
ClientScriptMan ager.RegisterFo rEventValidatio n method in order to
register the postback or callback data for validation.