I use Vista, and I have noticed this same thing. But I believe it is caused when I log out of my MS imail e-mail account.
If I have AL open in one tab, and my work e-mail open in another tab. When I log out of imail, click back to the AL tab, and select my next action - I will be logged out.
I guess I just attributed this to the the session ending in the window (possibly having an effect on the other tabs open in that window). This is the only way I can get this to happen. I could be way off though
