# Solution for Firefox 4 installation failure on Mac OS X due to 'libsmime3.dylib is in use' error

If you're attempting to upgrade to Firefox 4 on Mac and encounter this beauty

then you'll need to perform the following terminal commands as an easy workaround.

cd /Library/LaunchDaemons/    sudo launchctl stop com.cisco.anyconnect.vpnagentd    sudo launchctl unload com.cisco.anyconnect.vpnagentd.plist    killall vpnagentd

Now attempt to install FireFox 4 again before issuing the following to reconfigure VPNAgent:

launchctl load com.cisco.anyconnect.vpnagentd.plist

I've seen some other posts online suggesting that the killall command is sufficient, but that didn't work for me because vpnagentd was setup to automatically restart. The process I outlined here prevents that.