2002 Impala Security Light

It's been a year now since I've completed the resistor project for the ignition switch. There have been absolutely no issues for the past year with it not starting. Now the security light has been coming on once in awhile during driving until I turn the key off again. And just tonight my girlfriend said that the headlights and all the dash lights turned off while driving down the road for a second, came back on and the security light flashed and stayed on. She also said there was a click too when the lights came off and on. Any suggestions? Do I have to redo the resistors or could this be a deeper problem?? Thanks in advance for any suggestions!!

Please guys......Any help on this would be greatly appreciated. I just want to take care of this before it becomes a 'no start' issue again. Thanks.

Did the engine die when all the lights went off? I would look at the battery grounds for tightness and corrosion.
A failure of your resistors (I have the same mod on my Alero) while the enigine was running would not turn off all the lights, instead, the security light would come on steady.
I would look for a relay going bad. Consult your owners manual for the headlight relay location. Many of the relays are the same part number, so you may be able to swap it with another one and see if the problem follows the relay or not.