VCL is dead. Hasn't been updated since Sept 2013, and thus hasn't kept up with bugs/changes in the drivers. This is the main reason why we developed Hashstack. I assume the students that were working on VCL graduated, and thus it is now abandoned. Use at your own risk. If you do decide to use it, you're going to need to get some Infiniband hardware.
Edit: Just realized you said you had Nvidia hardware. VCL + oclHashcat only worked with AMD, not Nvidia.
Edit: Just realized you said you had Nvidia hardware. VCL + oclHashcat only worked with AMD, not Nvidia.