Having the same problem matey :'(
Just changed to 10mb AOL Cable Modem with Belkin 4 port router and WAS a full time WoW player during the summer periods but now it disconnects every 5mins :/ Not fun...
(Belkin F5D5231-4) and the new Cable modem thingy. Tried too many things - changing to static IP or turning off DHCP etc etc - but to no avail

-Thanks.
Ogre.