I guess the other person had a good one, you have two seperate accounts right?

you need to validate your internet connection, if you have DSL run one of the speedtests like DSL speed test
try opening a DOS cmd prompt and setup a ping to somewhere like yahoo ( ping -t yahoo.com ) then start your copies of wow and see if your internet dies.

Try un-overclocking your video card and/or motherboard, try disabling all of your addon's just for this test.

per say, you could have a bad internet, bad ram, bad video card, weak power supply.

good luck.