When trying to create world, it kicks me back to launcher

[CaptainSmacker06]

This is very weird, the first time I loaded Attack of the B team up, it went just fine. When I tried reloading my world, my game crashed and sent me back to the launcher. I've tried uninstalling it and reinstalling the modpack. I also deleted technic launcher and then redownloaded it, to find that the modpack creating a new world said creating terrain, then flickered with the title screen, and finally shut down minecraft and brought me to the technic launcher. Please help, I was having fun while it lasted. If this additional information is needed: this is happening with every modpack i have been trying to play after it happened with Attack of the B team.