It appears the root of this issue is;

Launching CMP from an HFS+ volume results in the runtime error immediatly, with the minimal entries in FileMon.

Launching CMP from a FAT32 or NTFS volume and scanning the HFS+ volume results in the same runtime error partially through the scan.

But using it with no HFS+ involved works properly.

I've come to the conclusion that using HFS volumes on Windows is like using HFS on an Apple IIgs. Forget it for anything you care about.