Sorry i should have been more clear, the ports are not forwarded at the same time as the DMZ.

Just to clarify, i`ve assigned my ps3 into dmz, via the dmz setting in the router, dhcp is disabled in the router as my other computers are assigned using a static ip address as i have ports that are open for each and require them to have the same ip address when the computer starts.

Pc 1 = 192.168.1.2 (single port forward assigned)
pc 2 = 192.168.1.3 (single port forward assigned)
ps3 = 192.168.1.100 (DMZ assigned)

would this confuse the router? *it confuses me sometimes *

Firewall is on on the router, you think turning this off may be worth a try. If so that would leave my puters pretty open, could you suggest a decent firewall if the hardware ones disabled?

Kind regards
si