Just to add another possiblity, has anyone reviewed the design 
of the "SecurityServer" in Darwin/OS X and its dealings with PAM? 

Documentation is sparse, but there's a few tidbits 
http://developer.apple.com/documentation/Darwin/Conceptual/KernelProgramming/security/index.html


-- 

The nice thing about Windows is - It does not just crash, it displays a
dialog box and lets you press 'OK' first.
						-- Arno Schaefer