Have you read the: Battle.net Connection issueshttp://us.blizzard.com/support/article.xml?locale=en_US&articleId=20792&parentCategoryId&pageNumber=1&categoryId=2645Quote
Step 2: Background Applications:
You may need to exit any programs you have running in the background to improve network performance and stability. For instructions on closing background applications, please visit the appropriate page below:
http://us.blizzard.com/support/article.xml?articleId=21052
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Step 4: Battle.net Server List:
Someone or something may have modified your server list so you are no longer connecting to a Blizzard Entertainment Battle.net server. For instructions on restoring the correct server list, please go to this page.
http://us.blizzard.com/support/article.xml?articleId=21138
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Step 5: Internet connection notes:
Firewalls, Routers, and Internet Connection Sharing
- If you are using any type of firewall, router, or you are sharing your internet connection between several computers, you may need to set your system up to allow access to Battle.net. For instructions on setting up your connection, please go to this page.