A former colleague from Airbus days was relating a story to me recently that was similar to bubbers44's story. Apparently a 737NG crew had been in cruise for some time when they realized that the WINDOW HEAT had not been turned ON prior to takoff, and was still OFF.
Without thinking, someone reached up and turned the WINDOW HEAT ON.
Immediately the outer pains heated up, "shock heating" occurred, and the four outer panes cracked...