There is a new way people are hacking WoW accounts. They insert a key logger into a banner ad that is running in the background on your internet browser. This exploit is undetectable by your browser or your anti-virus software. It only works for hacking WoW if you are on the infected site before you log into WoW. The key logger can then record you login information. If you open your browser after logging in, the keys you press in WoW would convey no useful information. I had several WoW related sites up yesterday so I can't be sure which one was infected.
Another recommendation ..... You probably don't want to run multiple tabs while logging into any site, including your bank.