Yep ML or 2 circulars because the stitches form around the cable, which is smaller than the needle.
Or move a few stitches back and forth so that the join between needles is not always in the same vertical line.
And make sure the second stitch of each needle is really tight (not just the first and last)
and it might help to make the last stitch on each needle a purl, and each first stitch of the needle a knit stitch (if your pattern permits).
Knitty also has a good article about reducing ladders I think.