http://eu.battle.net/wow/en/forum/topic/2793454326


also

...which may indeed be the cause of your latency issues.

As a first step, I recommend turning off the router for about 30 minutes, and then back on again. Once done, flush your DNS resolver cache:
Windows XP
- Click Start and then Run
- Type cmd in the run box and the press Enter
- In the black console command window that appears, type: ipconfig /flushdns
- After typing the above command, press Enter, then close this window

Windows Vista or 7
- Click Start, then Programs, then Accessories and then locate 'Command Prompt'
- Right-click on 'Command Prompt' and left-click on 'Run as Administrator'
- In the black console command window that appears, type: ipconfig /flushdns
- After typing the above command, press Enter, then close this window

If this does not work, can you try booting your computer into selective startup mode so we are sure there are no background applications interfering with the connection?
http://eu.blizzard.com/support/article/21288