CascadingDropDown and the Invalid postback or callback argument error

http://www.webswapp.com/codesamples/aspnet20/ajax/toolkit_cascadingdropdown.aspx

Thanks for the reply, I checked the source code of the demo webform and I found that EnableEventValidation is set to false, this means that there is no way having the ajax cascadingdropdown in a page with the event validation enabled? If I set it to true, I'll get the "Invalid postback or callback argument error"?

Thanks again.

You are right; the EnableEventValidation is set to false. I missed that part of your question. Hopefully someone from MSFT would post a solution.