Why won't Windows Live Messenger (MSN 8.0) start in Vista RC1?

Yesterday I upgraded one of my XP Pro SP2 systems to Vista RC1. Everything
looks amazing, and runs very smoothly(A lot better then Beta 2, or XP ever
did it seems).

The only real problem I've encountered, is that WLM fails to start. I
double-click it, and get the little circle thing for a few seconds... Then
nothing else happens. No error message, nothing. The application never
starts. But when I look in the process tray, I see that msnmsgr.exe is indeed
running, but the actual program is nowhere to be found.

I've tried many, many, re-installs; XP compatibily mode, you name it. But it
still does the same thing.

has anyone else ever had this problem?

Better yet: Does anyone know how to fix it?

I'd appreciate any information you can offer,

Thanks a lot!