I've had chain rub before, but this is a violent pop where it's catching on the pins on the inside of the chain ring. I had one of the mechs at the LBS take a look at what was happening and he agreed that it was excessive and unusual. Unfortunately I caught him on his way out the door, so we weren't able to really look into it any further.

This is enough that it causes a disruption in the pedal stroke, not just a bit of rubbing. It's bad enough that it felt like the chain was slipping. I know that this is a combo I'm unlikely to ever need (it's so flat around here I'm never even out of my big chain ring), but should it not at least turn the gear with just some rubbing, and not what feels like something physically trying to break?