Can you try enabling trace logging for the DatabaseServerLoginModule to prove that all of your values are set correctly.
I have just had a look at the code, the only reason why you would get the error you are getting is if after the query is executed an empty result set is returned.
Also you didn't say which database you are using, is there any way that you can enable tracing there to check what query is executed against the database.
SORRY, VERY SORRY
My own fault, I had forgotten to change the dsjndiname to the prodution db ups.
Once done all worked fin.
So once again sorry for wasting your time. But thank you for any reply.