Hi Eugene,
I've run DSSR on 5TGM as below, and the program works as expected. Since this is huge ribosomal structure, I guess your computer is running out of memory. What're settings of your system? How many GB memory do you have?
Command: x3dna-dssr -i=5TGM.cif --format=mmcif --idstr=long --more -o=5tgm0122.out
Date and time: Wed Feb 1 11:29:17 2017
File name: 5TGM.cif
no. of DNA/RNA chains: 10 [1=3151,2=1781,3=121,4=158,5=3152,6=1795,7=121,8=158,P=3,p=3]
no. of nucleotides: 10439
no. of atoms: 411545
no. of waters: 0
no. of metals: 2302 [Mg=1191,Zn=16,Os=1095]
# excerpt output on screen
total number of base pairs: 5079
total number of multiplets: 607
total number of helices: 304
total number of stems: 646
total number of isolated WC/wobble pairs: 264
total number of atom-base capping interactions: 619
total number of splayed-apart dinucleotides: 1322
total number of hairpin loops: 232
total number of bulges: 153
total number of internal loops: 329
total number of junctions: 128
total number of A-minor (type I and II) motifs: 199
total number of ribose zippers: 104
total number of kink turns: 13
total number of non-loop single-stranded segments: 101
total number of kissing loops: 10
Xiang-Jun