Gary,
Are you saying that just the water in the comparator tube is cloudy and even then only after you've added DPD? If that's the case, I can't offer a very informed opinion but would guess that it's still working OK so long as you're getting the color changes.

If the water in the pool is cloudy (which I don't think you were saying), this article by Ben may help: http://www.poolsolutions.com/gd/cloudy.html