Blog Entry: IE duplicate cookie problem
During testing of one of our applications, we found a problem with login to the site. Spent 3 hours debugging it, and finally concluded that server side software works correctly, but IE7 (7.0.5730.13) does not. IE7 sends two different cookies with same name. Usually this is the last thing which can come to your mind when you debugging your Web software.
As result, our server software reads first (invalid old) cookie, and the whole authentification provess is broken.
We were unable to find exact conditions to reproduce it: it just happens sometimes... The only way to fix it, is to restart IE completely (close all windows and start again). I will post updates if I find more information on this topic.
Update: One more reference about the same problem. So we know how to fix it, and going to do it now.
Final words: usually you investigate your own code to find the problem. Finding big problems like this in well known browser, is not really expected.