I had a problem with the 1.4.7 packs not launching. Turned out to be that I didn't have the path set right in the launcher options. I had it set to "./Packs" Instead of something like "C:\Users\RedBird\Documents\00 B3 Backup\0 Installed\Minecraft\FTB".
Could be another option that was set in the launcher that just isn't working for those packs.
I am not sure what might be doing it. Just going on my experiences.