So it turned out that it wasnt pfsense or the switches that were causing the problem one of the computer on the netword had a rouge DHCP server running which was trying to assign the LAN of pfsense an IP which screwed everything up. So it took alot of trial and error to find which computer. I found the computer but I have not had chance to look into the DHCP server that it is running.
Thanx everyone for their help