Well, I tried to play with your file (with 6-31G(d,p) basis set, for speed, but it does not matter).
First of all, your input geometry is far from being optimal. After optimization, both 1-2-3-4 and 2-3-4-5 torsions become substantially nonzero.
Second, in spite of warnings, PES scan runs successfully. If you remove (rather than set to 0) ORIG1 and ORIG2, scan will start with the values defined by $DATA. If ORIG1 or ORIG2 are set to 0, the scan will start with zero torsions 1-2-3-4 and 2-3-4-5.
>Black box methods are everywhere. You do know what I an talking about. And please, in this particular question, let me decide which approximation I need.
Well, don't be rude. It was a joke, I thought you understand :)
But seriously, I just wanted to say that you may try any other program. You don't actually have to do any calculations. If this alternative program manages to generate internal coordinates without warnings, you may use them in FireFly. If it fails, the molecule is really problematic and the only solution is to generate the internal coordinates manually. But after playing with your molecule I see that there is no problem at all.
[ This message was edited on Wed Dec 26 '12 at 5:00am by the author ]