I have had the same problem with my O5 since I got it new a year ago. At one point it would sound like it was being hit with a hammer on every serious climb.
The LBS tried a few things:
- Better rear QR, nipped up tight - no effect
- Tighten up the crank arm bolts - no effect
- Remove and grease the outside of the BB
Although not so bad since that last fix, the creek is still a bit irritating, but I am trying to learn to rise above it, Zen like, as the price I must pay in this imperfect world of suffering for an otherwise fantastic bike.