I have exactly the same setup (VM account with husband's email) and I'm having exactly the same problem. I did manage to set a non-virgin email to access virgin media email account. It sent through verification email. I clicked the link and managed to get in briefly. It gave errors about updating my security question so I restarted everything and haven't been able to log in since. It accepts the non-virgin email address I set up but won't let me log in (invalid email or password) and won't let me set a new password (Oops ... something went wrong. Please try again later.)
PLEASE SOMEONE HELP US to access our longstanding and constantly used virgin.net email accounts.