Mine front camera was also not working, the rear camera worked.
This was solved after replacing FLEX cable ( the flex cable comes with front camera, so its related to it )
i had that problem and i bought this and problem solved.
MOTOROLA DROID 3 XT862 LCD DIGITIZER FLEX CABLE KEYPAD FRONT HOUSING | eBay
also fixes black scrren on keyboard slide open
Sent from my bionic 4GLTE