The number of dial items is limited to, on an SGI at least, 18. There are 8 pre-allocated dial items (3*rot,3*trans,zoom,slab) which leaves space for only 10 torsion angles; if your ligand has more than ten torsion angles, the program crashes (not too elegant, I admit). Hence, the remedy: remove two of the torsions, or keep two sets of .torsion_information datablocks and toggle between them.
For example, you could create two .torsion datablocks, one with your ligand's ring torsions (call it .tors_ring) and one with the others (.tors_others); then create two little macros:
@ring t 3 72 copy_db .torsion_information .tors_ring bell message Ring torsions tor_res @other t 3 72 copy_db .torsion_information .tors_others bell message Other torsions tor_res
If you put them on your menu (menu @ring on menu @other on) all you have to do is click the appropriate macro to start "maiming" your ligand.