I Agree with Johnpoz, 0.0.0.0 - 126.255.255.255 used to be classed as 'Class A' but since the introduction of Classless routing such boundaries no longer exist.
in answer to BILTRITEPC, I can say pf2.0 has no problems with using 10.10.123.1/24 on the LAN if, I have built a test box and have just pinged it successfully for the last 10 mins without a hickup.
I use a 10.x.x.x/24 (Actually I have 4 of them) on my home network and they all work perfectly using PF2.0 to route between them.
Can you check that all settings are correct ie, lan DNS server is running, WAN DNS servers( listed in the general settings) are running and they can be used to resolve FQDN's.
what are the WAN and LAN ip's
Something is wrong and I would like to help.