Revit Family Opening - Error?

Your file is corrupt, and this is one of the worst errors to see since there is nothing you can do to restore it. You can try to send the file to Autodesk to recover, but it probably won't work. Your best bet is to rely on the latest back-up that will open successfully, and continue from there. If you don't have a back-up, you must start over. Typically this error is due to system crash or interrupt while saving. You'll also see this error if you've downloaded a file that was partial (the file upload didn't complete).