When I have had problems, it has been because the Sailwave file had fleets(starts) that are not PY. If these and all the competitors are edited out and the file is otherwise correct (dates etc) it works ok. If not you get a lot of garbage in PYS with message similar to the one you have got. Also if you accidentally send a race that hasn't taken place it gives an error. Is this your first attempt?
Mike Swingler
Flushing Sailing Club