WDDynamicRFCExecuteException

I have developed a sample webdynpro application which we intend using on both desktop and mobile device (HP iPac using Pocket IE 2003 or similar device). The application functions when executed from the desktop and PC Emulator (using the additional URL parameter sap.session.client=PieClient) , but on the actual device I receive the follwing error message when the BAPI is called:

"com.sap.webdynpro.modelimpl.dynamicrfc.WDDynamicRFCExecuteException"

Any assistance is greatly appreciated!

Regards,

Joanne