IntelliJ2017.1.2 with Scala SBT Run/Debug buttons greyed and unavailable

Everything was fine until... who knows what happened.

Have tried:

1. Updating to 2017.1.3
2. Turning off the "Use SBT shell for build and import (experimental)
3. Invalidating caches

Nothing seems to work. Log has the following error (just the pertinent bits):

2017-05-18 10:49:10,060 [ 792229] ERROR - penapi.actionSystem.impl.Utils - update failed for AnAction with ID=RunClass
java.lang.StackOverflowError
at java.security.AccessController.doPrivileged(Native Method)

Any suggestions?