Ray:
Yes, I made the change you suggested and things seem to be getting back to normal in the slip_Insert page, but the validation still allows for inserting second records for the same month without alerting the user, which it shouldn't.
Please try entering a record for username lulu and you'll see. Lulu already has records entered for the month of February, so the validation should send the user to the SecondPSMessage page, but it doesn't. It accepts the record.