This has happened to me intermittently, but not as consistently as is happening with you.
FWIW, I found the IE7 Beta 2 to be so buggy in general that I just uninstalled it in both XP x86 and XP x64 ...
I think you are experiencing a stability issue, and the reversion to the msn homepage may be some kind of self-repair feature.
I know that I'm thirsting for a new build, anyway (even though Opera 9 just RTM'd
) ...





I also started the 32-bit IE according to the shortcut and it does start up in the emulation mode.