Crashing while trying to start any mod pack.

I have been trying to get a mod pack started for the past month or so, but always end up getting the same fatal error in the crash log. "Patcher expecting non-empty class data file for net.minecraft.crash.CrashReport$1, but received empty." I have been through all the forums that I can find. I have deleted twitch, minecraft, forge, java basically everything that has to do with minecraft, and re-installed. I use the native launcher in twitch to launch the pack. I am trying to launch it for windows, also pretty new to troubleshooting these kinds of things. Any help would be greatly appreciated!