Locate the small red button on the bottom of the disposal. If it has popped out, press it back in. If it doesn't stay in, wait 20 minutes for the motor to cool and try again.
This is serious. If water leaks from the very bottom (motor shaft seal), the unit is dead and must be replaced. If it leaks from the sides (where the sink meets the disposal), it’s a plumbing seal issue. insinkerator troubleshooting guide