Zorua said:
Look at
this guide.
Also, it's not Treyarch's fault. It was the same with MW2.
i dnt want to sound like im attacking you, but no its not the same for mw2
My PS3 is NAT type'd 2 and MW2 im always Open NAT wise, but low and behold, Black Ops is always strict
@OP: I have tried many many many things, other than just NAT type forwarding and DMZ'ing it hasn't worked with me
Problem seems to lie with ISP's and Treyarch servers ALONG with PSN (so yeah imagine the possible problems)
there is though a possible fix for this issue, Insert MW2 (IF YOU HAVE IT) and get to the multiplayer menu screen (where you see your party etc)
there you should see your NAT type, from that screen eject the disc (dnt quite game, just press eject button) should be back @ XMB and insert black ops, you should have open NAT with working party invites and everything - i have done with many times and it works.
this is considering that your PS3 is NAT type 2 (which it should be more mw2 to have Open NAT in the first place)
Have fun.