I've installed Mavericks onto two main machines after testing it on one for a version. I'm not here to complain. I've had no major or unexpected problems. Until DP7, and I'd just like to see if anyone else could help me get to bottom of it. I described the onset of the problem at this forum dedicated to the text app Scrivener. Its project files were becoming corrupted with "zero length data" errors after a random but short duration of opening them. The actual text data was not lost inside the Show Package Contents folder, but the XML files were going haywire and losing the majority of their size. I thought it was just that one app. Then it moved to Scapple, a mindmapper by the same developer. Then some PDFs Then a photo! This has happened on a 2012 MacBook Pro Retina and 2009 iMac, both after updating to DP7. After a week (of increasing anxiety) I've just reverted both machines to DP6. But I think a .scriv project has just gotten corrupted again, on my main account's desktop under DP6 Opened another one and watched its size diminish in real time with the Inspector: 18.8 MB to 18.9 to 18.1 to 10.9 to 10.8 to 10.4 MB. I've repaired permissions. I've re-applied account privileges to my account. It would seem to be a system-wide issue that deals with the XML / file structure of documents. I can't discern anything popping up in Console for the system or the app. I can't think of any systematic changes outside of upgrading to DP7 a week ago. Just in case, I'm running Sophos Antivirus on my iMac. Both machines are on SSDs (one Apple, one manually installed) but I can't see this being a random parallel hardware problem. I'm testing a .scriv in a clean account on DP6 right now. After a few minutes it appears to be ok. (Fingers crossed!) So, what could cause documents (specifically documents: PDFs, XMLs, photo structure) to get corrupted with signs of actual data loss? Not all documents either. Usually just those recently opened by their respective apps, except for that one photo.