In the future, please post the actual error message, shown by clicking "Show details".
My guess is that it is caused by using "k" in the route instead of "K" which is defined in the symmetry points, although I'm surprised it even manages to run the band structure calculation without errors, in that case.
Else post the error message and also state which version of VNL is used.
I should also point out that your are trying to use hexagonal symmetry points in a rectangular lattice - you will probably not get the results you anticipate...
