Hi Sean,
It is likely that you've not properly set up 3DNA v2.0. Did you run [red:1nrkjhgd]x3dna_setup[/red:1nrkjhgd] as documented in the 2008 3DNA Nature Protocols paper?
More specifically, what's the output from running the following:
echo $X3DNABy default, if the [mono:1nrkjhgd]X3DNA[/mono:1nrkjhgd] environment variable is not set, the program will use [mono:1nrkjhgd]$HOME/X3DNA[/mono:1nrkjhgd]. That explains the error message:
[pre:1nrkjhgd]open_file </home/seanlaw/X3DNA/config/help3dna.dat> failed: No such file or directory[/pre:1nrkjhgd]
HTH,
Xiang-Jun