SkrubWorm,
I've had a similar problem, roughly since updating my OS to High Sierra. My CCleaner Pro takes roughly 30 min to fully execute, then several hours to remove files. After about 45 min I'm prompted to enter an admin password. Safari files take longest to process; Firefox second longest; Chrome, Opera etc go relatively quickly. I thought the app was entirely broken, but it's just interminably slow.
It is exceedingly frustrating that Piriform now seems to regard Mac users as marginal. If it's going to drop Mac support, have the courtesy of informing (and refunding) us.
