When an exception is being thrown and its not on the 'List of Exceptions' we can look at some documentation included with the Yellowfin Install. The documentation file you would want is named WebServiceException.html. This Can be located within the Yellowfin Installation directory itself at, <yellowfin>/development/doc/webserices/javadoc/com/hof/mi/web/service/:
This document is useful if you are not sure what might be causing a webservice exception as well.
Once there we want to access the 'Constant Field Values'. This is the fastest way to get to a list of the numbered webservice exceptions in your current build of Yellowfin:
Above is the list of WebServiceExceptions in my local installation of Yellowfin. The Constant Field is the name of the exception and the Value is the number error code associated with it.
I hope this helps identify any unknown WebServiceExceptions.