Either have return values set when calling functions or have internal 
handling of errors.  Currently, if an element id in the response is not 
found in the registered elements, you just get a javescript error in the 
function _processAjaxElementUpdate.  Either the processing should stop 
for that element or there should be some kind of a return code to the 
calling sendRequest to handle the error gracefully.

I agree. Especially for us ajax/javascript newbees. I took me a while to 
realize where my error was because RICO simply returns with no message.