I'd take that link down if I were you. The FTB team doesn't like it when the launcher is redistributed.The problem is not the launcher. its forge. The forge was made for a 1.4.7 jar and it is detecting a 1.4.6 jar. go to where you keep the files. so if you are using the all i have created. Here for Mac the it is in the Content>Resources>Java>(Mod Pack The Problem Is IN)>minecraft>bin. Delete the bin file and when you reload the ModPack it will ask you to Update ModPack say yes. This should fix the problem.