I have a 2811 running 12.4(11XJ) Adv Enterprise and I cannot remote static nat entries. I have tried a reboot, taking off the nat inside/outside interface commands. Any ideas. It is bizarre.
Likely bug CSCsg84883.
Try repeating the "no ip nat .." many times in rapid succession, a colleague of mine succeeded this way.
If still there, the only option is to save config to a file, edit out the nat command, copy file back to nvram (conf over), reboot.
hope this helps, please rate post if it does