Had the exact same sort of thing happen with a Dunlops tyre I had a few years back (when it was only a couple weeks old). Not good when you look at the car the morning after a late night mega-thrash and see that sort of thing!! Took it back and kicked up a stink and they ended up replacing it for free..
Was a couple of weeks later that I remembered I'd actually hit a silent cop with that wheel about a week before i noticed the problem.. Oops!