You are receiving the message "Recipient address rejected: User unknown in virtual mailbox table" as it appears that the account nightvisions no longer exists. Neither does phantasmagoric, as both cannot be found in the member search on the forum. I checked for phantasmagoric as I thought the change might have been successful in the end, but it appears to have been completely unsuccessful. My best guess is that you deleted your account on accident.
You could do what Morgra suggested above, but if it doesn't work out for you in the end, then my personal suggestion is waiting until registration opens to create an account with the e-mail that is now possibly no longer in use. That, or you could recycle any other account you may have into the new username you're wanting. I have noticed maybe once or twice before that people with yahoo e-mails seem to have the most issues. I don't know if this is a coincidence or just bad luck. I hope this issue mends or gets resolved for you soon, corvus.