If it wasn't making a noise originally, then it's unlikely to be anything stepper related.

Now don't take offense at the following questions, but I like to cover the basics.
What bearings did you fit?
Support block should be two angular contact 7xxx series bearings, not standard deep groove 6000 series.
And did you fit the bearings the correct way around, with outers races opposing/inner races facing?
And did you adjust the preload correctly?