Make sure you're opening the right ports for your PS3. If you're opening the xbox 360 ports on your router, this won't be successful for the PS3. Also I've noticed if I run my PS3 & xbox 360 at the same time my PS3 is moderate NAT and xbox is open. They do share one or two ports. Let me know what you've done and how I can help.

i havnt ran the ps3 and xbox at the same time, went to port forward.com chose my router, thompson alcatel tg782t, then chose playstation network and followed all the steps, ps3 always runs on strict, xbox always on open, opening the ps3 ports didnt change a thing, ps3 still running on strict, also should mention that i only have the problem with black ops, do prefer xbox but still like to play zombies with a couple of ps3 friends but on strict i cant even join them. used to do the mw2 trick to get my nat open but that wont even work anymore.....