Game Kills My Internet

have you tried the laptop with the same network cable?

interesting...once you exit wow, you have zero connectivity?
A stretch, but have you done a virus malware scan?
Can you ping your router/isp gateway?
any new software installs recently?
running any weird wow mods?

if you arent infected with any sort of virus or malware...
start a command prompt and type
ping google.com -t
this will create an endless ping (hit ctril+c to stop it)
run wow in windowed mode, attempt to login, and watch the ping replies and see exactly when they stop.
after the internet dies, go back to your command prompt and type "netstat /a"
look for any tcp conenctions that are in a close_wait, fin_wait or time_wait state. Check the ip's of said connections and see if they are related to your isp, or the wow servers.
make a note of the ip addresses in this state.
reboot.
run a tracert on a couple of them and see if they die at any point. Ping a couple of them, see if they respond.
this is just to verify conenctivity, seeing if there is anything unusual happening between you and wherever else.

try uninstalling any wow mods, just run wow in vanilla mode.
have you rebooted your cable modem?

just some suggestions.

-l