Unable to type in Arduino IDE running on OS X I'm trying to use the Arduino IDE (1.6.8 downloaded from arduino.cc) on a MacBook running OS X (10.11.5 beta).

The IDE seems to run and I can open and upload the examples and they run. But…

I can't type in the editor window of the IDE – either with the examples or with the new sketch that opens when you launch the IDE.

I have a similar problem with the version of the IDE distributed with mBlock (1.6.5) if I use the Edit in Arduino IDE button. I also tried the 1.6.9 hourly version. All to no avail. So I'm thinking that this is a OS X problem, or maybe an issue with version of Java (1.8.0).

Any ideas or troubleshooting suggestions?
Make sure that in preferences the option Use external editor is not checked.