You might have changed your registries somehow, check that.
Addition: To do that:
Go into the start menu and click 'Run...'
type in regedit and click ok
Go into HKEY_LOCAL_USER->Software->Battle.net->Configuration
Double click 'Battle.net Gateways'
It should say:
CODE
1001
02
uswest.battle.net
8
U.S. West
useast.battle.net
6
U.S. East
asia.battle.net
-9
Asia
europe.battle.net
-1
Europe