Same exact issue, different modpack. From what I can tell by looking at the console as FTB tries to launch the modpack is that it can't connect to download the updates and ends up on running on any backup version of the modpack you have on your computer, hence the "not installed" portion of the disconnect message. Moving the existing modpack from the install directory results in the launcher basically stopping midst the launch as it's trying to download the pack. Someone with the same issue, in a previous thread, mentioned it might have something to do with an "md5" issue ... or something. I'm not sure what's going on myself, but I really hope we get some clear help with this. :S