FBinNY's post still has me curious if the outer plates are cracking and splitting, or if the pin is pulling out and separating from the outer plate.

Got any pictures? Are you using the same 9-speed chain on the LHT? Despite your humility, I'm finding it hard to believe that installation error could be the problem, since you've managed so many miles on other bikes without a problem. Perhaps Andy is on the right track that you've simply gotten a couple of chains from a bad batch.

EDIT: Simul-post with FB's latest!