I've been surching for a solution to that problem on many discussion like: http://forums.esri.com/Thread.asp?t=221032&c=121&f=1377&ESRISessionID=DK8wwPwCeLk7ng4Doa3mkPCte9F-Mm9XtZ5nczpcNG2ekB8MPiLVLWONn4qbFdjUSRwQrFlYdBs%3D.
I still cannot find an issue to that problem: the floodplain delineation needs a Water Surface Tin to be created. I could skip the problems of converting tin to grid for steps before by creating grids with 3D Analyst, but this cannot work for the floodplain delineation creation.
I'm working with the latest version of georas 9.2, SDF to XML works fine. I've been trying installing the service pack but nothing is changing...