random?
I have experienced this at random intervals from time to time on all my cpanel machines... never seen the problem outside of my cpanel machines.. so either my other machines don't get enough usage, or it's something cpanel specific... doubtful it's related to cpanel.. but who knows.
Anyhow, definately recommend writing a script that checks for it and kills it off.. just be careful not to kill real vi instances that users are working with that happen to be in startup mode, which can shoot the usage up to 99% for just a second.