Hi
D-Link have real problems getting all aspect of their firmware working correctly, there is always something that doesn't work. It is a real pity as this could have been a really popular router if they had just fixed the advanced features in the setup interface.
Once the filters are applied have you tried rebooting the router to see if they take effect?
Another problem is you can't use Inbound filtering rules on Port Forwarding, meaning that the Inbound filtering options are almost worthless. You can on their other boxes, not this one, apparently they know about the problem but still not fixed. Also despite the options to email a log, you're never receive one, and the Guest wireless SSID that has now finally appeared after a year of the feature being removed is a complete waste of time as you can't set a password on it and it provides full access to the local area network, not my idea of a Guest wireless network! Turn the Guest network on and you might as well just have removed all security from the normal wireless settings and used that instead.
You can go back don't worry, it's a little bit more effort but you are not stuck on 2.51. Download the
original firmware and unzip it ready to use.
1) You must connect by wired cable to Ethernet Port 1.
2) Manually set your computer to use IP address 192.168.1.10.
3) Turn off the D-Link, then using an opened paper clip press in the reset button on the back and hold it pressed while turning on the router. Wait for around 5 seconds until the power light goes red.
4) From the computer connected to Ethernet Port 1, open a web browser and go to 192.168.1.1 and you should see a simple browser interface asking for some firmware, point it to the original firmware and wait for it to flash and reboot.
Undo the manual changes for the IP address on your computer, and then flash back up to the version you want.
You could miss out the step of flashing to the original firmware and at that point use the firmware version of your choice, however I have found problems with this method sometimes and going back to the original then back up seems to work every time.
Make sure you raise it as an issue, it's not the first time I've read of complaints with the filtering, the more that complain the better chance of a fix.
Regards
Phil "