Hi and welcome,
But please search before posting.
That 'Fix' (mind the quotes) has already been posted 7 months earlier,
and there are also already threads about this error...
eg:
Suyesh's reply to Error 8000401a - Windows Live Messenger 2009 (14.0.8050.1202)
However, this is in no way an official fix and may well cripple more stuff than you think.
I can not verify it at this moment, but I have a very strong feeling that simply
deleting your contact cache instead (in the proper way) will resolve the same issue. And deleting the cache does not cripple any other stuff; it simply instructs Messenger to rebuild the list from the servers. Unlike this registry key which possibly cripples other stuff as well (now or in the future).
/ 
