Just to add, I've found a similar issue on my Windows system here.
I having just upgraded from Windows XP to Windows 7, I notice PM took a few seconds to color classing/rate a photo..
A few minutes to do a few photos (50-100).. eekk. also found any tagging I did was not saved .. hmm
I found the fix or issue was the security permissions on the files and folders.
See when I upgraded I formatted and installed Win 7 on my system drive.
I have my photos on another drive in the system. I never touched during the install of Windows 7
I as soon and I changed the security permissions, removing the "unknown user"(S-1-5-21-....) and making my new user owner.
PM started working nice and quick. also saved the color classing/rate etc...
Maybe this is the same for Mac.. ?? don't remember all my unix* permissions. :|
rgrds,
Mike
info:
Photo Mechanic 4.6.5 on Windows 7 x64 (v6.1.7600) on a Intel(R) Xeon(R) CPU X3360 @ 2.83GHz, 4GB RAM