Perhaps the link got corrupted somehow. You might try reloading your home page if it works fine from a 'favorite'. Go to your Yahoo page using the favorites, then I'm not sure exactly what MS calls it, 'cause I use Firefox and I go to 'Options' then click 'Use Current Page' for a home page. It will be something similar.
In your address box, manually enter "http://my.yahoo.com"
Or enter "www.yahoo.com" and select "My Yahoo" from the Sites List on left.
If it loads, reset that as your home page to overwrite your current setting.
I think, there is something up with Yahoo as I've been having trouble for weeks. I have a mailbox that I use infrequently because I'm part of several Yahoo groups. Anyways, everytime I go into check my e-mails it freezes up on me. I've even tried deleting some old e-mails to free up space even though it says I have a ton but that isn't helping.