I had to make a Friendly Neighborhood IT Guy call last weekend when my friend's Yahoo! mail broke. Surprise, it was the IE10 mandatory Windows Update. AT&T acknowledged the issue was on their end and gave my friend $30 off per month for the next six months of their U-Verse package. For my part, I installed Chrome and Yahoo! mail was back.Problem resolved by uninstalling Windows Update "Internet Explorer 10" Go figure