There is a BUG in Outlook 2007 build 12.0.4518.1014.

I have TWO profiles, and very often when I start with the non-Default one,
and then close it and restart Outlook 2007, I no longer have a choice to
select which profile to start it with. The only way to fix that is to go
Task Manager, and manually kill OUTLOOK.EXE and then restart it. Then, it
works fine.

They need to FIX this annoying problem. I tried finding where I can submit
a bug report, but could not find anything of sorts on their website.

P.S. I am running Vista Ultimate together with this setup.