Kirk,
I've just recently noticed that Photo Mechanic's contact sheet view is not displaying some of my PSD's, but unfortunately a re-install of QuickTime did not solve my problem.
Initially the file's thumbnail is displayed but then quickly reverts back to a banner that displays "The layered Photoshop file was not saved with a composite image". I've double checked my preferences in Photoshop and confirmed that "Maximize PSD compatibility" is set to always. I've re-saved a couple of files to help ensure this is the case.
I'm using V4.4.3.3 under Windows XP SP2.