If you're using a Power Mac G5 computer with three or more displays connected, you may notice that in Final Cut Pro, the Playback Output section of the the A/V Devices tab doesn't show more than the first two displays.
This happens because Final Cut Pro does not support having more than two computer displays connected to the computer. To fully control Final Cut Pro, make sure that you only connect up to two displays at a time.
For more information, see article 302671, "Final Cut Pro supports up to two displays at a time."