We have a patch for binary version ready (see here: https://answers.unrealengine.com/questions/12530/mac-os-1092-mavericks-launch-editor-u4.html), but I’m not sure when exactly will it get to GitHub. Sorry for inconvenience! For a quick fix, you can move IOHIDManagerOpen call and error check from lines 77-86 to earlier place of code, after IOHIDManagerCreate call and check, so to line 20. This should help.