I would try the following:

Kill the power to the unit completely. Leave it off for about five minutes, then plug it back in. This will cause the microprocessor on the logic board to reboot. It might clear the problem.

If that doesn't work, I would put in a new light bulb or bulbs, as the case may be. I know that sounds weird, but trust me, I have a reason for the suggestion.

At least some of the Sears openers use electronics to directly control the lamp(s), instead of using a relay. That means the bulb's filaments are part of a circuit. It is remotely possible that some abnormal characteristic of the bulb is causing issues for the circuitry.

It's a long shot, but it doesn't take much effort to give it a try.

If neither of those work, you are probably looking at a flaky logic board. If that's the case, it will have to be replace. You can usually order one over the Internet for $60 - $70.

Buying a whole new unit might be a better deal when Sears has them on sale.