Microsoft has pushed IE8 as a critical update (you may already be running it), which under certain conditions requires the use of a special Update Blocker tool (provided by Microsoft) if you don't want it on your system yet.  (http://blogs.msdn.com/ie/archive/2009/01/06/ie8-blocker-toolkit-available-today.aspx)
The fun doesn't stop there kids.  Upon installing IE8 on your system, Microsoft updates your default browser back to IE!  (http://www.pcworld.com/article.....rnet_explorer_8.html)  Who cares what you want to use, Micro$oft knows best.