Digital BW, The Print

> So as weird as this seems, would there be any logical reason for
> this?

If the only thing that changes is the image capture device, then the
image capture device is the source of the problem.  You may have a
defective CCD on the digital camera.  Lines in a digital image are
defects in the CCD; perfectly straight lines in a scanned film image
that are consistent from image to image and from film to film are
usually defects in the scanner (again, in the CCD of the scanner).
Non-perfect lines in a single roll of scanned film are usually scratches
on the film, and most lines on film come from lab carelessness during
development.  If lines appear on many films from the same camera but not
on films from other cameras, there may be something in the camera that
is scratching the emulsion.

There are some other remote possibilities, like unusual interpolation
artifacts in the printer (a possibility if you are getting the same
lines from two different digicams, especially if they both have the same
pixel dimensions).  Another possibility is a defect in the printer that
is masked by the grain of most film scans but is easier to see against
the normally grainless backgrounds of digicam photos.  It would have to
be extraordinarily subtle to show only on prints from digicam shots,
though.