This must be boring everyone, but John Embretsen asked:

Maybe I've missed something, but why won't it work to set the property in the 
application (Java code), before loading the embedded driver?

// App startup....
System.setProperty("derby.stream.error.field", "MyApp.DEV_NULL");
// DB startup...

Well the answer is that it *does* work. And I suppose the real question was why I hadn't tried it, but nobody really wants to know the answer to that.

Thanks John. Problem solved. I do appreciate the way professionals suffer amateurs like me on these lists.

David

PS
Now, does anyone know how to include a derby database in a Windows .exe file? 

(And does anyone know how to replace the generic Sun icon on the top left with one's own application icon. Can't expect the helpful folks from Sun to answer that, but if I were a Windows Java developer I'd want to know. Or, then again, perhaps it's the sort of thing only Mac veterans like me worry about.)