The call to the asyncronise method has changed from (userparameters, onComplete, onTimeOut, onError) to (userparameters, onSuccess, onFail, userContext).

Obviously this is an improvement as you can now track userContext of the Webservice calls.

To fix the above message make sure you are defining your userContext even if it is null. For example:

 <script language="javascript" type="text/javascript">

 var userContext1;       

 WebContentFlow.AJAX.ContentflowAJAXAPI.BuildPage("String parameter",onSuccess,onFailed,userContext1)      

 function onSuccess(result,userContext,sender)        {            alert(result);        }        

 function onFailed(result)        {            alert("Failed request >"  + result.get_message());       

}