This exact same thing happened to me. Suddenly, the unit was beeping, and I looked and saw that it was counting down the power settings from power, 10 to power nine etc. etc. and then recycling… I found this string. JKnox’s Post inspired me to try something… I lightly tapped on the keyboard, striking the areas between the number pads and the other buttons… Several times… Apparently that loosened whichever button was stuck in the closed position and the keypad started working.