NIS2012 - Smart Firewall button/status greyed out

Since updating to 2012 I have noticed a couple of times after my PC boots up that the button (on/off switch) for Smart Firewall in the 'advanced' panel is greyed out.

 

The button itself is still in the 'on' position, and norton still displays as secure/green, however the button is simply greyed out and unusable (as in I couldn't turn it off or on if I wanted too).

 

I'm just wondering what this means and why it seems to occasionally occur.

 

Thanks for any help.