I got this working, what you need to do is download the 12.09 (final?) AA build from http://downloads.openwrt.org/attitude_adjustment/12.09/ramips/rt305x/ or you could go for the bleeding edge at
Choose the "factory.bin" version for your first flash (e.g, openwrt-ramips-rt305x-dir-615-d-squashfs-factory.bin version )
when you flash in the future you can choose the upgrade.bin
Go to your DLink Router, take the power plug out, and put & hold a pin/paperclip into the reset button.
Put power on (keeping the paper clip in)
and the front light should start flashing orange in a couple of seconds.
At this point the router is in failsafe, emergency mode
On your PC (macs are similar though), set your IP Address to 192.168.0.10, subnet 255.255.255.0
From a browser (i used chrome and it worked fine, but I hear IE might be better), navigate to 192.168.0.1
This takes you to the "emergency room - flash loader)" website. At this point you can provide the factory.bin and voila flash away..
Leave it 5mins or so.. When the flashing is done the router will reboot and the lights will flash green. At this point reconfigure your PC to use DHCP and then navigate to 192.168.1.1 to access openwrt.
Should all work fine.. best of all the D-series are pretty much unbrickable as the emergency room bootloader is in rom (or something similar) not flash . .awesome
Let me know if this works for you