Yahoo email logging in problems.

Ever since I installed Avast I have been unable to get into yahoo email.
"If you do not accept the cookies set on login or your computer is not configured to accept cookies, your session will expire almost immediately. We use cookies (small pieces of site information) to assist us in user authentication and in saving configuration information. Cookies are required for Yahoo! Mail. "

I am running windows XP Home edition. I have turned off webshield with no success. I have installed avast and it worked. I have reinstalled and … its stopped now.

I have put IE settings to allow all cookies. No joy

Any suggestions ?

Will this help?
http://forum.avast.com/index.php?topic=14854.msg238394#msg238394

Sometimes this is because the yahoo mail url is on the blocked sites of IE (see security tab of settings).