Hi Ken,
Glad you are getting collation results! Yes, Graphviz is required for the variant graph display. It should be available as a package you can install on your server if you are running a linux distribution, the Windows VMRCRE download bundle has it packaged in, and if you are running a Mac, you can get a package from our download folder: http://crosswire.org/ftpmirror/pub/vmrcre/ (or likely find a newer version somewhere else online).
If you still have trouble getting variant graphs working, let me know the environment on which you are running and I'll try to help.
Troy
