There is allmost certainly nothing wrong with the Firefly installation.
There is however a bug in the em driver ( the driver used for the Intel NIC’s ) in version 7.0 of Freebsd. Which causes corruption of UDP packets ( used by Bonjour/mDNS ) if checksum offloading is enabled ( this is the default ).
Solution is to disable checksum offloading for your network interface.
To disable checksum offloading type the following command :
ifconfig em0 -rxcsum -txcsum
To disable checksum offloading on the next reboot add -rxcsum -txcsum to the ifconfig_em0 line in /etc/rc.conf
I had the same problem when I updated my server form version 6.3 to 7.0.
You can also update to version 7.1 which doesn’t have this bug
It seems the em driver in FreeBSD 8.0-STABLE has the same or similar problems. My firefly-svn-1696 fails miserably due to unknown (network) reasons.
Having disabled checksum offloading things seem to work properly. See how long this lasts 8)