heya,
The DHCP client in this case is a Billion 5200 ADSL2+ modem.
In this case, I restarted pfSense, and it seemed to work, sort of.
Sometimes it'd work fine.
Otherwise, if I I started it up, and then plug in the DHCP-serving modem, the WebConfigurator would sometimes become unresponsive - and even the VGA console on the server wouldn't respond to keystrokes. Since I couldn't get in via the web interface, console, or SSH, I didn't really have a way to retrieve /var/log/system.log ???. However, the pfSense server would still respond to pings.
Anyhow, I've ended up trying out pfSense 2.1-BETA0, and that seems to work ok with DHCP.
Cheers,
Victor