Check from adaware / spyware and see if your pc is clean.
I'd update any packages you use adaware/spybot etc then go offline and run them. I've had issues from that in the past, mainly on ET but once with wow, usually if I've been near u-tube amusingly.
Checking your pc case & gpu fans for dirt and using a brush to remove it would also be an idea as they do pick up crap, and eventually that can lead to crashes and it running a bit slow. Spyware of something system based, as mentioned above that is hogging memory sounds more likely though. Also check all your fans are running ok, in case a component is causing the system to overheat.
If still iffy I'd strip your WoW mods out, then gradually add them back in, in case it is a mod issue. I've warily kept clear of ace2 and running a ace 2 setup as I got bsod & crashing and very laggy gameplay/fps when I swapped mods after installing a 8800 GPU. From swapping back to titan/Bongos I've had far more stability and only one crash. I surmise a mod had a memory leak, caused the pc to chug then killed it. Took a while with having decent ram, but was occuring faster in instances. Shame as some of the nice clear interfaces on show here look to be ace2 based and I don't fancy the risk.
Former TBC/LK Tank
Waiting for Dunmail Jnr to sleep to enable online gaming.