Great, thanks for your patience! 🙂 It took all day, but it looks I have a decent solution to the corrupt error messages. Will post again when I do a release tomorrow (doing a release a then going to bed is always a bad idea!).
Ok, 1.8.12 is up now and should fix the error messages so I can fix problems more easily. Unfortunately I had to do another mandatory launcher update, though this time it only affects OS X. Hopefully now I can focus on the actual app. Updating the launcher is extremely painful!
Can you try again and post the error?