You probably changed nothing.  The flashing lights are showing were the image is completely blown out - the flashing areas are completely white (255, 255, 255).  The camera is just warning you of this fact.  If the rest of the image is exposed properly, than it is nothing to worry about.  If it is flashing in the sky where you want detail - the clouds, for example, you will need to shoot the image again with some negative exposure compensation.

(If the problem is worse than you remember, you might have some positive exposure compensation dialed in.)