By ‘old’ do you mean that you have had these addresses for some time, and secondly are you still an active VM broadband customer?
The reason I ask is that continued use of any of the VM branded email addresses (including the ntlworld ones) are dependent on you being a current customer. If you no longer are, or have moved or left Vm and later rejoined, then there is the distinct possibility that the email address has been, or in the process of being,deleted.