After the blackout of 2003 was done, a friend called me because he could not use his Brother HL1240 printer. All the LEDs were flashing and it would not print. I found this and it fixed it for him. Hope it helps someone else in the same trouble:

Resetting the printer should clear the flashing lights.

How to Perform A Factory Reset:
Turn the printer off.
Hold in the circular button on the front of the printer.
Turn the printer back on.
When the DRUM light is lit by itself let go of the button.
Hold in the circular button again.
Once the Alarm light comes on, let go of the button.
This has performed a factory reset on the printer.

If resetting the printer still does not clear the error lights, please call our toll free customer service line at 800-276-7746, Monday through Friday, 6:00am to 4:00pm, Pacific Standard Time for repair options.