Thanks for getting back to me.
The scenery path is: /Volumes/Elements/Old HD/FlightGear/w010n50.tgz
This didn't work, so I made another scenery folder/Volumes/Elements/FlightGear Scenery/w010n50.tgz but this still didn't work.
If I copy it to my main hard drive it works no problem, but I don't like to keep it there for numerous reasons.
Elements is my external hard drive.
PS My iMac is Sept 2011 21.5 2.5GHZ with ATI 512MB, Snow Leopard (don't like Lion, memory leaks, lol) with 8GB of RAM