Hm... changing NAT seems to be trickier with D-Kink for whatever rason. Some digging around found someone claiming D-Link told them it can't be changed.
Ah well, an alternate solution may be in order. Go into the PS3's settings and find the IP address given to your PS3. Then, in the Advanced tab of your router settings click on DMZ. Enable this and put the last numbers of the IP address in the blank, then hit the apply button. This puts the PS3 outside of any protection the router may give, which should allow all traffic.
An update of the router's firmware may help things along as well. You can find details about that at D-Link's site.