are you using your primary paypal account email to recieve payments? If not try switching to that
I think I am, but then I don't handle the PayPal payments, so I PM'd that person to doublecheck.
When I view the details of the payment in my PayPal log (as a buyer), it shows the email address as membership@lsjc.org, and money sent to as custsvc@lsjc.org. I've tried it with both and I get the error both ways.