So on my 1999 Sububran...all of the sudden the 2 rear doors are not able to be unlocked or locked by the key fob or pwr door lock button on the drivers side control...if it was just one door i would think the servo for that door failed...but its both doors at once...when i hit the button its like i can hear & see them twitch trying to lock or unlock but the lock switch on the door just won't move....again its strange that both rear doors hit at the same time...

Any ideas ? or has this happened to any other members ?

 

I'd be my guess that the master switch is possibly flaky, might want to see if you can clean the switch on the drivers door. if there is some movement my thinking is that the voltage is too low due to a dirty switch making poor contact..
Might try pulling the connectors off and just reseating them also...

 

If that doesn't work, start checking for a broken wire.