Sammy, so your saying that when you hit the back page in IE the page that you just came from says the page has expired? Don't you get a prompt that asks if you want to still refresh? I have this happen every once in a great while, but it always says this page has expired, and asks if I want to try and refresh it.
Do you have an updated version of IE?
Are you up to date on all the BS Windows/IE updates?