https://www.dropbox.com/s/qgt1o8w7tjwcpje/Screenshot%20from%202014-09-14%2015%3A54%3A10.png?dl=0

I think that explains it all.

Edit: Sorry, I forgot to try with an updated buildcraft. I'll reply and/or close this if it is fixed.

I think that explains absolutely nothing :P Try to clean your config folder and update BC.

As I said, I will test that. As for the screenshot, it does show that buildcraft tries to make the folders oddly, as the blueprints folder is started directly above the minecraft running directory while including the running directory's name.