Don't know if this helps your situation any, but when I put a set of SPD pedals on the mountain bike, one jammed and absolutely would not release. Had to take the shoe off to get out of it, after I took a tumble down a hill.

Turns out the cleat on the shoe was loose, and one of the mounting screws hanging down got jammed in the pedal's release mechanism. You might try turning the bike upside down and wiggling the shoe back and forth, that's how I finally got them unstuck.