According to Marty at the Windows Live Messenger team blog (MessengerSays) anyone using a version of Windows Live Messenger (either a version 8 or a 8.1 beta) will now be prompted to update when they sign in.

Last week we reported how people using previous 8.1 beta version we being prompted to update, but the updates were wrong and stated that a new BETA version was available - not the final version.

Judging by a screenshot posted with the blog post at MessengerSays it appears that this error still exists. This is understandable if the text for the update checker is coded into the program (all though it means that the programmers probably didn't think that the next version after the last 8.1 beta would be a final version) but if the text is retrieved from a remote server then this is a careless error, and could very well affect current version 8 users and tell them to upgrade to what they think is a beta, which they may refuse to do.

In the same blog post Marty says that the final version of WLM 8.1 has been downloaded over 60 million times, and that the download rate is continuing to increase, probably mainly due to update prompts.

Since Thursday all users of Windows Live Messenger 8 or an 8.1 beta should be getting an upgrade toast on sign in that tells them of the availability of the final version of 8.1, and over the next month they will be widening the update to all MSN Messenger and Windows Live Messenger users running Windows XP or Vista.

(... and in case you were wondering, yes - news is slow at the moment)

Source: MessengerSays blog post