Many thanks for your reply Absorbation. Hear what you are saying, I do however run this particular version on other installations without any kind of issues. Usually, with older unspported versions (as you are aware), login failure is accompanied by a message instructing the user to upgrade which I do not get.
I will have a go with a newer version. In case this does not resolve my problem, are the various registry edits provided in the thread below relevant.
http://shoutbox.menthix.net/showthread.php?tid=20295
Appreciate that in some cases fixing msn messenger seems to be more a 'black art'.
Cheers