[igraph] Error: "At iterators.c:721 : Cannot create iterator, invalid vertex id, Invalid vertex id" while computing shortest path

[shahab mokarizadeh]

Hi,

I invoked  "shortest.paths (graph,row) " function in R in order to
compute shortest path in the graph. But I get the following error
after a while:

Error in shortest.paths(my_directed_graph, i) :
  At iterators.c:721 : Cannot create iterator, invalid vertex id,
Invalid vertex id
In addition: There were 50 or more warnings (use warnings() to see the first 50)

Any idea about what would be the source of error??
Thanks,

/Shahab