I am having the exact same problem. I am running Minecraft 1.6.4, and trying to install Forge using the latest build (9.11.0.883). I've tried installing on a clean install of 1.6.4, get the error message "These libraries failed to download. Try again. org.scala-lang:scala-library:2.10.2, org.scala-lang:scala-comiler:2:10.2." I have downloaded the libraries.zip file that lucas1998 provided the link for, and extracted the file to my .minecraft folder, but still I am getting the same error message.
BTW, I am running Mac OSX 10.6.8, if that makes any difference.