Ubuntu – urxvt uses pink instead of solarized until I run xrdb ~/.Xresources

Edit: I discovered, that this seems to be a bug in Ubuntu: https://bugs.launchpad.net/ubuntu/+source/unity/+bug/1163129 – Any idea how to fix this by myself?

I just want to switch to urxvt, but I have a strange problem with my .Xresources. When I log in and start urxvt, everything is pink in pink and I get these error messages

urxvt: unable to parse color 'S_base0', using pink instead.
urxvt: unable to parse color 'S_base03', using pink instead.
...(repeated for all colors I defined)...
urxvt: unable to parse color 'S_base03', using pink instead.

However, once I ran xrdb ~/.Xresources, all newly opened urxvt's are fine and beautifully solarized. WAT?

My .Xresources: https://gist.github.com/iGEL/6880992 – I'm using Ubuntu 13.04 (64 bit), but installed the package rxvt-unicode-256color from Ubuntu 13.10 to get the current version of urxvt (9.18).

Edit: Notice that the colors are defined in the same file they are used. Maybe urxvt (or whatever is reading the .Xresources) can't parse and use the variables in the same run? Looks however like an odd idea.