When you try to sign in to webmail ( https://my.virginmedia.com/my-apps/email/mailbox ) - do you get any error message? If it is the message "mailbox unavailable - try again", then wait here for a member of the Forum Team, who will take your personal details by private message and see what is needed to get you working again.
Also, please try changing your password. Sign in to My Virgin Media, go to My Profile and/or Manage Accounts depending on whether the account concerned is your primary account or an additional one. Select the account concerned and then click on Change to the right of password if a primary account or View/Change then change to the right of password for secondary accounts.
After things are fixed, you may also wish to check your auto forwarding and filter rules which may have been set up in your webmail. Also we would recommend doing an anti virus scan on all devices that you are trying to access the impacted email account from.