Compiler Error CS0030 with Ajax
When using Ajax Pro, you have to add the runat="server" tag on the form to be used. In other words, you have to have at least one server-side form in the class whose type is to be registered as an Ajax class. Otherwise, you'll end up with a Compiler Error CS0030 Error Message Cannot convert type 'type' to 'type'. It took me almost an hour troubleshooting this.
Read the complete post at http://alexrazon.blogspot.com/2006/09/compiler-error-cs0030-with-ajax.html