I recently managed to mess up my Mac mini while resetting PRAM and NVRAM. I did reset them indeed but something got corrupted because the mini would hang at the blue screen with the spinning beach ball re-appearing time and time again. Strangely I could still connect to it with SSH and file sharing worked, too.
I tried lots of things such as resetting the System Management Controller (SMC) and booting from the Snow Leopard install DVD to verify and fix permissions/disk.
I found an interesting post in the Apple forum from someone whoes log file showed the same type of errors:
Login Window Started Security Agent
Login Window - Returned from Security Agent
AuthorizationRef returned errAuthorizationDenied. Exiting.
The post mentions a “corrupted authorization file” but that didn’t help me much (where is this file?). Googleing for that lead me to a blog entry labeled “LoginWindow crash” which explains things quite detailed. A second hint came from the insanelymac.com forum, thanks.
In the end you need to replace the authorization file at /private/etc/authorization with either
- authorization~previous in the same folder
- or the one from the OS X install disk at /Volumes/osx/private/etc/authorization