Using the Aether II launcher? Getting this error when trying to play?
It's a pretty easy fix, but make sure you do all of this with Minecraft closed!
Navigate to your .aether folder. .aether is where all of your Aether II data is stored if you use the Aether II launcher, and it can be found in the same place as your .minecraft. If you're on Windows, you can get to the .aether folder by pressing the Windows key + R and typing in %appdata%\.aether
Once your .aether is open, go to profiles, then 1.7.10-1.5.1, and finally, open the mods folder. Once you're there, all you have to do is delete the file named aether.jar.
Now, you should be set to reopen the launcher once again and play the latest release of the Aether II!
If you've followed the steps above and are still having issues playing the Aether II through our launcher, we recommend performing a manual installation. We have nifty guides for installing the Aether II manually both on the normal Minecraft launcher and MultiMC!
Apologies for the issues!