I've had the same and only issue since i installed Mountain Lion, and it only happens when I try to save an image or webpage. Sometimes it works and other times the pinwheel appears and then Safari shuts down. I've reported the issue via crash report to Apple each time. No help so far. I don't think Java has anything to do with saving an image or webpage/document, and if it does, shutting it off doesn't let me use Twitter which is the only Social application I use other than Imessage.
Thre are no messages in Console that indicate anything. When it has a problem the only info seems to appear in the crash report.