There is a MSN Messenger 8 Beta running around but you can only get into the beta if you receive an invitation via email. It is not yet in the public beta phase.
There is a so-called security risk in MSN Messenger 8 beta. If you use MSN Messenger 8 beta and receive an IM with a link to a leaked "MSN Messenger 8 Beta" from a friend in your list; then don't open it!
Security firm F-Secure is warning about this new worm that spreads from a fake website, where the author pretends to have a copy of MSN Messenger 8 beta.
The download BETA8WEBINSTALL.EXE from that fake site actually installs a worm that will by turn send instant messages to everyone on the user's MSN list with links to download their "beta". The malware also connects to a bot network.