Guido Jansen

No idea. I'll ask my son to start testing, after removing the resource pack. I did do already a complete reinstall of yosemite and that did not help.

See log attached. This is a crash where there is no black screen, instead the crash was forced using the method you suggested, F3+C for 10 seconds.

Same problem here. Needs a fix, my son just powers down the computer to fix it.

There is no way to exit the black screen from the mac, at least not that I could find. However, I can ssh from another computer to the imac. I can then kill the loginwindow process belonging to the minecraft user. Just killing the java and minecraftlauncher does not fix it.