This is a Forge error with 1.5.2 in order to set up Forge, it tries to pull some java libs it needs from a site and those files are no longer available. Download this file https://bitbucket.org/luacs1998/forg...fmllibs152.zip and extract them into the minecraft folder in your HappyDiggers FTB instance. You can also find this info here: http://www.minecraftforge.net/forum/...opic,20.0.html under "Common Problems and Solutions".