May 28, '13 07:30:00AM • Contributed by: poenn
As it turns out, FaceTime is dependent on a correct logic board serial number. This is also true for other services like iCloud. This particular Mac had its logic board replaced a long time ago, and the technician forgot to set the serial number on the new board. So instead of the regular serial number it said SystemSerialNumb in System Profiler. After setting the serial number to the correct one, which can be found on every Mac's housing, FaceTime would log in and work flawlessly.
In case you are wondering: every Apple Authorized Service Partner has access to a bootable image which contains a tool to write the serial number to the logic board.
[kirkmc adds: Interesting point. I recall having had a logic board change some years ago, and the serial number was not set (as I discovered when the Mac needed to go into service again). This was around the time that FaceTime was launched, and I could never get it to work on that Mac. It's too far in the past to be sure, but this might have been the cause.]
