When you tell it to install certificate does the error come back when you close out of IE and go back to the site? Try clearing your temporary internet files and cookies... It could also be the site you are trying to visit's problem...I am an IT guy and have seen this before...in the worse cases, even though the problem really doesn't hinder you and doesn't mean anything detrimental, sometimes it requires a rebuild of the O/S because reinstallation of IE doesn't even work. So if none of the pointers I suggested work, then you could live with it, try reinstalling IE, or rebuild your OS...Hope this helps