To be honest I have never used xft, also, I don't use xdefault, or Xresource as it's called on my system. However, I did some reading and found that you can test it to see if it would work from another terminal. So try this code first from a terminal and see if urxvt starts with the font.
urxvt -fn "xft:lucida console:pixsize=9"
Or change pixsize to whatever size you want.
I tested this with liberation serif and it worked.
If you can, post the name of the font file you are using, and where you got it from and I'll try it out myself.
<Edit> I just found something else. Perhaps the font wasn't installed. I came across this problem with one of my fonts and just found a solution.
Try "fc-cache -f -v" to update your fonts.