PayPal validated my member ID and said there's nothing wrong with it. Their technical support went through my actual web-site and got the same error that I get. We were able to send a PayPal payment request to the ID and all worked fine...so the ID does work. We cleared out my Cookies and Temporary Internet files. We changed the primary email address on the account and re-tested it...still same error.
Are you able to de-bug my website WITH my member id?
The id is new...firstname.lastname@example.org...can you use this for your test to see what might be wrong?