I remember having this problem, it's caused by only IE for a change not executing the page on using the back button instead the last cached version of that page is displayed. our fix was to set the cache expiry of the page like this:
Response.Cache.SetExpires(DateTime.UtcNow.AddMinutes(-1));
Response.Cache.SetCacheability(HttpCacheability.NoCache);
Response.Cache.SetNoStore();
hope it helps.