Windows Mail in Vista

[Snoo]

Something very strange has happened - when I wish to forward an email to other people, and I go to SELECT RECIPIENTS, to add them, the list is now blank -  not a recipient in sight! I have absolutely no recollection of deleting them all - and I am sure if I had accidentally gone to do that I would have got one of the famous Windows messages popping up saying 'do you REALLY want to do that?'! So I am at a complete loss as to how it happened and how to get them all back again! Anyone got any ideas, please?!