Actually when I changed from wireless to wired my nat type was the same (moderate). After using DMZ my nat type changed to open for both, so i don't think it's just wireless. Also DMZ is basically a last resort as you are vulnerable to security risks. People imply that since its a ps3 system it doesn't use (.exe files) so you're fairy safe but I'm just going on opinions here. If you want you can try post forwarding first at this site:
If that doesn't work then you can try DMZ, but as I said before it's a last resort. Good luck
NAT type is not affected by wired or wireless. Being wired will give your connection more stability compared to wifi.
All the how to's are at the bottom of the article.
Read the Elagaphant article to check your router MTU setting.
My guess would be that your IP address for your console changed and the port forwarding that you have in place actually worked against you as it locked those ports to your old IP address. I'd check that first. Look in your internet connection menus and there should be an option to display your settings.
Edit: My second thought would be a loose cable.