Moved this to Firewall Enterprise for better handling.
I suggest you call in to Support and do a remote session so we can see if you have the DHCP Relay rules set up correctly on the firewall.
You can use these commands to help you troubleshoot:
-- Shows you the zone numbers for each zone name. The following commands only display the zone number from 'region.'
$> ifconfig bridge0 addr
-- Lists the addresses learned by the bridge and shows which interface in the bridge saw that IP/MAC combination
$> ifconfig bridge0 flush
-- Flushes all the learned addresses
$> ifconfig bridge0 maxaddr [size]
-- The default size is 100 entries in the bridge table. You may or may not have to increase this someday.
$> arp -an
-- Shows your arp table
$> route -n get [IP address]
-- Shows which interface a packet would go out if it is destined for [IP address]