We've seen this problem crop up with a couple of other members. Unfortunately, we can't isolate the problem. Seems to be account-related; one work-around we've used is to have the member create a new account. We then merge the old account into the new account and rename the new account to the old username. Kind of a kludge - you have to reset all your personalizations and you're "Memeber Since..." date is reset to the new account.