#7 - June 3, 2009, 10:39 a.m.
We have been having some reports on this.
My first two recommendations are in this order.
First, try rebooting your system entirely. That's fairly quick, easy to do - and some players have reported that has worked.
Next, if rebooting doesn't help, please try flushing your DNS. Instructions on that can be found here.
http://us.blizzard.com/support/article.xml?locale=en_US&articleId=21014
Please do let me know if neither of those seem to help.