Thank you for the suggestions, Joan and Gornot. Joan, I made sure that I am automatically going to the my.msn.com home page, and I am, so that is not the answer. Gornot, I am not positive on how to make sure the browser does not delete my login cookie. I checked settings in Tools, Internet Options, and didn't notice anything, although I am far from expert in this and perhaps I missed it. If you can suggest a specific setting I should check, I would be happy to do so. I did add msn.com to sites listed in the privacy tab, but that did not help.
So I am open to further suggestions as to why, since my upgrade to Win 7 from Vista, opening IE 8 to my.msn, no longer auto logs me in.