Google first! :-)
Like here:
http://gaming.stackexchange.com/questions/133219/scala-library-error-when-launching-forge-for-minecraft-1-6-4
scala-library.jar Is renamed to scala-library.jar.stash.
Also bcprov-jdk15on-148.jar is renamed to bcprov-jdk15on-148.jar.stash
Just download thme manually, rename and put in the library folder ...