As well as macjack's suggestions, there is also this file you can try deleting:
"/Users/yourname/Library/Preferences/com.apple.systemuiserver.plist"
I have not run the Security Updates (and don't plan to, I generally wait until they are part of a complete OS update, and 10.4.9 will be along Any Day Now), so I can't comment on whether they could have messed up something. I did look at the things that SystemUIServer is using in ActivityMonitor (select a running process, click the Inspect icon, then click the "Open Files and Ports" tab to see what's what) and I see that SystemUIServer is consulting two things involving Security:
/System/Library/Frameworks/Security.framework/Versions/A/Security
/System/Library/Frameworks/SecurityInterface.framework/Versions/A/SecurityInterf ace
Both the Security and SecurityInterface binaries I have were last modified on Oct 4, 2006, which is when I ran the 10.4.8 update. You could check yours and see if they have been modified more recently.
Francine
Francine
Schwieder