It is inescapable that you will, from time to time, run into i-snags with your site uploads. Some sites start all over if a publishing operation fails, and some behave even worse. Sandvox, however, is much more resilient. If the internet fails you in the middle of an upload, just click Publish again. Anything that's completely uploaded at the time of failure won't need to be uploaded again; Sandvox only uploads during the second Publish operation what didn't get all the way up during the first one.