The problem appears to be due to an error in Apple's routines that create a disk image. QuickBooks is telling it to make a backup that is big enough to hold the company file and any attachments (if you have that option on). However sometimes the disk image isn't made large enough.   We have a possible fix for this but haven't released it yet.  Contact me (my email address is next to my name above) and we'll try to get you a build to try to see if it corrects it.