Just thinking out loud here...
Do you run on a particularly grippy surface? Concrete? Race track quality or hard, coarse asphalt? One thing to possibly suspect is flex in the trailing arm or the mounting points. If you're placing a significant side load on the car, and the chassis or suspension is flexing excessively, it's possible you could be placing too much of an axial load on the CV.
That it seems to be occurring on only one side implies a possible external cause.
If this makes sense, I'd check the trailing arms and trailing arm mounts for any signs of flex/fatigue/wear/cracking. Either that, or you're running your courses on part of an oval track, and use the same banked turn at most events...
Just a thought...
-Josh2
So maybe it would be a lot safer for him to go the opposite direction at the track next time? Seems like you would be dodging traffic all the time???