Mac Mini Server running Mountain Lion (10.8.2) is freezing during boot (last line: IPv6 packet filtering initialized)
A possibility

The lack of progress, beyond the firewall-related message, may be unrelated to the firewall or networking. For example, these two lines from Intel Mac Pro Stuck on Gray Apple screen before OS load (2010-07-17): 

IPv6 packet filtering initialized, default to accept, logging disabled
Jul 15 22:08:39 kextd[25]: kextd_watch_volumes: Couldn't set up diskarb sessions


– that's not to say that your issue may be the same; just to encourage thinking beyond networking. 

Preliminary advice

Use Recovery OS: 


Disk Utility to verify the file system of the OS X startup volume
verify permissions of the OS X startup volume.


Then – if the file system is OK – get the full installer for OS X (at another Mac, if necessary); install to the outdated Mac.