Yes I use the same computer every time. I am not aware of the cache clearing automatically and I have no idea about the cookies. How do I check that?

My problem with the messages is not that they don't change color but when I go "back" to the index they lose the "read" color and revert back to "unread". And it doesn't seems to happen to all of them. Very strange but what else would you expect from a computer that started its life with Windows ME and is now XP.