dotty version 96c (09-24-96) lefty version 10 Mar 2005 graphviz version 2.8 (Wed Dec 20 14:50:18 UTC 2006)
[erg] This is actually an error in dot during mincross.
This is a bug which we have to fix, but it is related to the many flat edges in your graph, induced by setting
constraint=false in most of your edges. Is this the effect you really want? If not, removing the constraint=false
attributes should allow the graph to be laid out.