This is happening when adding a breakpoint for all exceptions, and I see that these exceptions are normal behavior with CoreData: http://stackoverflow.com/questions/8337635/nsmanagedobjectcontext-exception-breakpoint-stops-at-save-method-but-no-log-c/8913045#8913045
The solution is just to create a conditional ‘all exceptions’ breakpoint to filter out CoreData program flow exceptions.
