When I click on my favorites for Yahoo Mail I get to enter the password and then I get a HTTP\400 not found error. If I use the laptop and do the same thing it works fine.
It is obviously something in my desktop. The only thing I've had done was to add a 3TB external drive and to switch my C: and D: drives to use the faster and larger 1TB vs 500GB as the system drive.
Everything else seems to be working fine.