Tomorrow, I use mediawiki with IE8 from Ko NyiLynnSeck laptop.Don’t work this address http://localhost/mediawiki/index.php/MainPage . It work in Firefox and IE7. I think, this is apache problem. I forget to one test. I should try with index.php?title=MainPage. I think it may work.
about IE8 : http://blogs.msdn.com/ie/