[modeller_usage] umber of equivalent positions < 3

Hi Everyone, I am getting this error, when i am running modeller. i posted this mail before but i did not get any reply. looking forward to it

Traceback (most recent call last): File "compare_1.py", line 32, in ? aln.malign3d() File "/usr/lib/modeller9v8/modlib/modeller/alignment.py", line 329, in malign3d edit_file_ext) _modeller.ModellerError: fit2xyz_296E> Number of equivalent positions < 3: 1