Same here, (OS X 10.8.4 MBA 4GB 256SSD 1.8Ghz I7) it crashes always upon exit in standalone mode and when used as an AU plugin (MainStage). I think it might have something to do with memory. 4GB just isn't enough. It's not crashing that often on my older iMac with 12GB. Could someone with 8GB MBP / MBA confirm that it's working so I could buy a new Mac?