OS X stopped letting me install any software not coming from Apple. I wanted to update some software, and instead of seeing the “Quarantine Dialog” box telling that the software was just downloaded from Internet, I got a dialog box telling me that the software was corrupted.

In fact, it was not corrupted—I could use it on another Mac. The issue wasn’t affecting Apple software, only third-party apps. Only by setting the “Anywhere” setting in System Preferences -> Security for installing apps could I install software again. But I didn’t want to use that setting.

Looking in the Console, I saw error 99999 from CoreServiceUIagent when I tried to install software.

CoreServicesUIAgent[2105]: Error SecAssessmentCreate: L’opération n’a pas pu s’achever. (OSStatus erreur 99999).

After some research and help from Apple I found that a specific file’s corruption was the source of my woes.

A way to confirm that y …

Source: Mac OSX Hints