I added Kotlin support to Android Studio, but did no other Kotlin related steps. I then did an Android Studio update to V2.3.2. After that, ADB failed to initialize when trying to run an existing Java based project, and Android Studio froze. Killing the adb processes in Task Manager unfroze Android Studio.
To fix the problem, I uninstalled Kotlin, reinstalled Kotlin, then clicked Restart Android Studio. Android Studio froze trying to restart, but killing the adb processes again allowed the restart, and ADB integration now works with Kotlin installed.