Launcher Problems

[SiriusEdward]

So I installed several modpacks for my modded minecraft, but it turns out that none of them will actually launch. Every time I start the launcher and play the game it gives me an error message:

[00:24:41] [main/INFO]: Loading tweak class name cpw.mods.fml.common.launcher.FMLTweaker
[00:24:41] [main/ERROR]: Unable to launch
java.lang.ClassNotFoundException: cpw.mods.fml.common.launcher.FMLTweaker
at java.net.URLClassLoader.findClass(Unknown Source) ~[?:1.8.0_101]
at java.lang.ClassLoader.loadClass(Unknown Source) ~[?:1.8.0_101]
at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source) ~[?:1.8.0_101]
at java.lang.ClassLoader.loadClass(Unknown Source) ~[?:1.8.0_101]
at net.minecraft.launchwrapper.LaunchClassLoader.findClass(LaunchClassLoader.java:106) ~[launchwrapper-1.12.jar:?]
at java.lang.ClassLoader.loadClass(Unknown Source) ~[?:1.8.0_101]
at java.lang.ClassLoader.loadClass(Unknown Source) ~[?:1.8.0_101]
at java.lang.Class.forName0(Native Method) ~[?:1.8.0_101]
at java.lang.Class.forName(Unknown Source) ~[?:1.8.0_101]
at net.minecraft.launchwrapper.Launch.launch(Launch.java:98) [launchwrapper-1.12.jar:?]
at net.minecraft.launchwrapper.Launch.main(Launch.java:28) [launchwrapper-1.12.jar:?]
Java HotSpot(TM) Client VM warning: Using incremental CMS is deprecated and will likely be removed in a future release

Does anyone have this problem and get it solved?

 

[lenscas]

assuming the good old ftb launcher is being used
options->force update->launch the modpack

 

[SiriusEdward]

I don't think it's the problem of that because I'm kind of new to curse, I think I got the latest version of curse though.