This is what I did to get this solved,
I had two ntlworld.com accounts which were working great until Yesterday. No problems on Outlook 2007. Tried to open outlook and kept asking for username and password.
In the end I went to my virgin media and created two new email addresses
name@virginmedia.com
Then logged into the ntlworld.com accounts then changed email settings and set them to forward all emails to the new virginmedia address
Went back into outlook 2007 and set the accounts back up again as per carmad's email changing the @ntlworld part for @virginmedia and it is all working fine now.
Seems a bit stupid to have to do this but at least I am not going to loose any emails. Hate webmail.