Network Settings in System Preferences greyed out

This is the Network item in the main view in System Preferences that's greyed out?

Or is this something within the Network setup?

Has anything happened to this OS X system recently? Installed some software or tools? Upgraded it? (Did anything in particular change prior to this greyed-out setting?)

Is this OS X system associated with and being managed from a server? Or is is this a standalone OS X system? (If you don't know what I'm referring to here, then this configuration is probably standalone.)

Have you tried booting from the installation DVD (10.6 and earlier) or via the Recovery Partition (10.7), and then (via the Utilities Menu) launching Disk Utility and performing a permissions repair?

And about the version, the sequence:

 > About This Mac

will tell you the version.

My first preference when any antivirus tool is involved is to acquire the official removal directions and/or the removal tools directly from the vendor and to completely remove the package, repair permissions and disk structures, and reboot.

As for your sequence, ensure you have clicked the padlock in the lower left of the main page of the Network Preferences display (if the padlock is not already shown as being open) before you go into the Advanced settings.

Click the lock icon in the lower left corner of the window and authenticate with your administrator password.