Xbox live and connection problems?

I just bought a new Xbox 360 slim this wednesday and i have been wanting to play games like black ops with my friends. well when i had my ps3 i was able to play with my friends until one day when i tried connecting to a friend and it wouldn't let me. idk what happened. and now with my xbox, i still cant play with any of my friends or even connect to a party. i opened up 4 ports on my router (btw i have a linksys router.) i have 3074 both, 88 udp, 53 both and 80 tcp open. when i test my connection it says it connected to everything and when i back out of the network screen and go back to the network screen, it says everything is unknown. i also have an error status report of W:0000-0021, X:0000-F001, Y:20A8-4840, Z:0000-0000, ID:FFFF-FFFF. and im able to play online all the time, just not with any of my friends. idk what my nat is cuz i cant seem to find it anywhere on my xbox. i also have dmz enabled and upnp enabled. im unable to hardwire my xbox cuz my modem is in my living room.. id appreciate any help getting my xbox up and running correctly cuz its really starting to upset me. i havent been able to play with any of my friends since october-november ish..