I found this free for personal use RSA encryption utility for Live/MSN Messenger called SimpLite. I'm just testing it out now and it seems to work really well. And it supports the latests version of Live Messenger even though it doesn't say "Live Messenger". It will automatically make conversations red that are unencrtyped and make conversations that are encrypted green. Both ends need to install the utility but its a very quick download and a simple install if you follow and read the wizard. It uses 2048 Bit RSA keys so I figure it's pretty secure.