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.