I believe that some of the issues with IE not keeping people logged in is that we where using a very large value for the cookie expiration time and IE just "doesn't like it", it hasn't for quite some time; you can play around in Google and find plenty of people talking about it with other products. 7.5.8 lowered this timeframe (I think it's a week now versus a year) so IE should "play nice" with at least that part of the equation now.
