I run a compact double crankset with a triple derailleur. Sometimes, when the cable tension drops even slightly, that chain wedge thing will happen. It happens on DH's bike too, and he's running a compact double with a double derailleur. In fact, it happened on his bike on today's ride. Half a turn on the downtube barrel adjuster, and problem solved.

I'd double-check the tension before doing anything else...

Good luck!