We do not currently provide any support for Messenger Plus! Live, which is in closed beta testing stage. You are not an official tester of Plus! Live, so there is no reason you can be using the leaked beta of it - Please uninstall it now. If your friend is not an official tester of Plus! Live, you should tell him to uninstall too. As is your experience, the beta Plus! Live is unstable and contains bugs, and it's not worth you getting baffled by it.
If you can't live without Plus! when using Messenger, you'd probably want to uninstall Windows Live Messenger 8.0 and go back to old MSN Messenger 7.5, which there is an official Messenger Plus! 3.63.148 supports. Or you have to wait for the official final release of Messenger Plus! Live, sorry.