believe it or not but this has actually happened to me, when i will get "strange" frame rates i jump ALL video settings up and crank the card.

I have an 8800gt superclocked edition. The card has had some weird functions within it. If wont "jump" to the super clocked mode if the computer does not feel like its being pressed enough so its potential is harnessed. When i jump all the settings up it almost scares the card, turns on superclocked, and performs with better frame rates.

Weird but its happened a number of times.

Also ctrl + alt + del, and see what things you are running in the back ground, very excessive things are not needed, some say a firewall is necessary, i havent heard of anyone getting a virus while playing wow. Turn off some back ground applications and see how it works,

Lastly, update your drivers, that should be as common as brushing your teeth.

gl.