This has happened to me on a number of occasions...
As you know, BPL sends us an email whenever a member PM us -- and we reply by clicking the link embedded within that email. But sometimes, when I do that, I get an error message -- something to the effect that the sender is no longer a registered forum member! And when that happens, I have to look for the member's name here on the forum, click on it, and PM my reply.
Do you guys get this error message from time to time as well?