Parental controls issues with 10.6.8

Hi,

I use Parental Controls to restrict activity on my son's account.

I have a list of applications that I allow him to use - Safari, Firefox, Printer etc.

As of few weeks ago several applications (like Firefox) stopped working on his account. Whenever he start it mac osx asks for permissions. I always select "Allow always" and nothing - application does not start and it asks for permissions again and again and again. Eventually I give up. I then find that Firefox is not in the list of allowed applications (even though it was there before). I add it again and tried the same from his account - no luck.

In the system log I find this message :

Jul 12 20:56:54 imac-win parentalcontrolsd[13037]: -[ActivityTracker checkApp:csFlags:] [982:<USERACCOUNT>] -- *** Failed code signature validation: /Applications/Firefox.app/Contents/MacOS/firefox

Jul 12 20:56:54 imac-win parentalcontrolsd[13037]: -[ActivityTracker checkApp:csFlags:] [1036:<USERACCOUNT>] -- *** Incoming app appears to be masquerading as white listed app and failed signature validation: /Applications/Firefox.app/Contents/MacOS/firefox. Note: This may be a valid app of a different version than what was whitelisted (on a different volume?)

Jul 12 20:56:54 imac-win com.apple.launchd.peruser.504[13055] ([0x0-0xa1aa1a].org.mozilla.firefox[13096]): posix_spawn("/Applications/Firefox.app/Contents/MacOS/firefox", ...): Permission denied

Jul 12 20:56:54 imac-win com.apple.launchd.peruser.504[13055] ([0x0-0xa1aa1a].org.mozilla.firefox[13096]): Exited with exit code: 1

Any ideas ?

biribenda