Pontiac Repair: 3.8L engine, pontiac bonneville, gm motor

Question
I have a '99 Pontiac Bonneville with a 3.8L Series 2 Engine, and 159,000 miles.  I took it to a mechanic for a loud knocking noise that occurred suddenly.  They discovered that the lifters are bad in it.  They say they can find no reason why they went bad and have never heard of them going bad on this particular engine.  We have always used name-brand oil for oil changes and have it serviced regularly.  Do you know of any reason why this would have happened?  Have you ever heard of this happening with this engine?  

Answer
I have actually heard of this once before and everyone thought it was a strange occourance then too. It was on a different GM motor though, but not too far off from your 3800. As far as why this happened, the mileage isn't excessive but is a factor, have them check to make sure oil pressure isn't dropping too far down because that is what keeps the lifters pumped up and working. Unfortunately this may have just been a rare thing and totally unavoidable. Sorry I can't be of better help than this but hope it ends well for you.