well, this actually happened to me, if it says connection failed right after you press login, then i think i can help.
all you have to do is right click your time display in the task bar on the lower right of ur screen, then click adjust time/date and make sure the time and date are correct.
my problem was because i came back from vacation after the new year, so when i went to reset my time/date, i accidentally put january 2008 instead of 2009, so i corrected it today and right away AIM was working for me