Error with Amorphous Cell

Hi, I am trying to put 50 molecules into an amorphous cell, it fives an error message:

ERROR: Torsions must be defined around a bond

I never met this error before, it seems new to MS 7.0.

I don't understand why I have to define a torsion for amorphous cell calculations even I have clicked "Calculate torsion automatically" and Include non backbone torsions" in the option tab.

Thanks for your help!

Leon