My yahoo mail is not accessable at the usual place I click to get my mail. Yesterday I upgraded to explorer 8?

Yesterday I upgraded to explorer 8 and since then I am having this problem. I ususally click at the the top left of the yahoo page where all the catogaries like Mail, auto, finance , etc of Yahoo page is displayed . At the top of the category is yahoo mail. I click here because it shows me how many emails I have got. When I click at this usual spot on the page I get an error message stating "Explorer cannot display this page " . It says further the diagnostics have revealed no hardware problems and just try rerefshing or ( F5 ) . I tried this & nothing happens. Finally, I had to go to google it to get at my yahoo mail. Whats going on here ??? Can some one help ??? Yahoo page ( my Home Page )comes up OK on start up and the news etc & everything else is Ok. Its only this Mail feature upsets me.