Can't type/delete in IntelliJ Idea, OSX El Capitan 4

I had the same issue when upgrading to IntelliJ 14.1.4.
If you have the IdeaVim plug-in installed, try disabling it. That worked for me.
Here are instructions if you have never disabled plugins before: Enabling and Disabling Plugins

Turn off Vim Emulator from Tools in the intelliJ: