Today I tried to install Firefox 4 only to be notified that libsmime3.dylib is in use. What the heck is that!?!? A quick google tells me that Cisco's VPN Agent uses it for the vpnagentd process. Cool!
sudo killall vpnagentd
That should do the trick. NOT! The problem is soon as I kill vpnagentd the process restarts. Well, if you are experiencing the same issue I faced then here's the trick.
sudo launchctl unload /Library/LaunchDaemons/com.cisco.anyconnect.vpnagentd.plist
Instead of restarting the process this will actually unload vpnagentd from launchctl and prevent it from starting back up. Once you have successfully installed Firefox 4 then all you need to do is reload it back into launchctl.
sudo launchctl load /Library/LaunchDaemons/com.cisco.anyconnect.vpnagentd.plist