I think this is a bug in the remote searchTask() service. I have seen that java.util.Date gets transferred to the server as GregorianCalendar and probably is not getting properly converted back.
Said that you will need to file an SR to get this addressed.
Meanwhile to overcome this you can try instead java.util.Date to pass an epoch number of milliseconds instead e.g. java.util.Date.getTime(). I think it will be able to convert millis to Date when searching for mathching tasks
Alex
#webMethods#MWS-CAF-Task-Engine#webMethods-BPMS