It would have been a CID's (Cabin Interface Device ???? Can't remember) reset which during it's reset cycle switches all power off to the cabin to enable a full systems reset, test and recycle.
Doesn't take long, ground power to the flight deck is unaffected and generally seem to do the job.
Most likely it was a spurious smoke warning which generates a CID's Caution which has to be checked or extinguished (the caution that is) before flight.