Wow:Cataclysm using too much cpu with new video card

System specs:

Intel Pentium 4
6 GB RAM (Three 2GB sticks- one slot is currently empty)
Windows 7 64-bit
Brand new Nvidia GeForce GTX460 graphics card
750W power supply

I replaced my Nvidia 9800 GT because of some driver compatibility issues crashing my system that I was tired of dealing with (tried for 2 weeks to fix it, gave up, took it to a computer repair place, they couldn't figure it out, I finally said screw it, I'll just get another video card). Wiped the hard drive with a fresh install of Windows 7 last night. Installed the new graphics card today and while running Wow:Cataclysm, the CPU usage jumps to 90%+. Frame rate stays above 40fps, 60fps outside of major cities. No other processes are running. It tends to spike at 90% in waves, dropping down to 40-50% for a few seconds then jumps to 90% for a few seconds- repeat. Didn't have this issue with the previous 9800 graphics card. I'm not sure what the issue is. When WoW is not running, CPU hovers between 5% and 12%, peaking at 30% every 15 seconds or so. I'm at a loss... any help would be much appreciated.

-Lindsey