Unable to change NAT settings?

Hi, I play Xbox live and for some reason I have a hard time joining other peoples Chats/Games/Parties... and I posted on a forum and he said I need to change my NAT from Strict to moderate or something else... He sent me here
http://portforward.com/english/routers/port_forwarding/Linksys/WRT54GC/Xbox_Live_360.htm
and i followed those steps yet it continues to stay at Strict.
I also tried going straight from the wall to the 360 but it's still strict, would it be my ISP which is Optilink (Local Service)
Im using a Linksys Wireless WRT54GC router... I am connected by Cable to the Xbox 360.
Any help would be great!