The most direct solution is to abandon using DKE to convert your DICOMs.  Just do it using dcm2niix and generate your own bvecs, or try using MRtrix to convert everything:  http://www.mrtrix.org/, or DSI Studio.

DKE is not commercial software and random user-end changes (like file naming) can lead to errors.  

Slow down, step back, and think carefully about your acquired data and what DKE can accept as input data.  The more you understand the fundamentals, the quicker you'll achieve results!