Well, I have been trying more things. However, I now appear to have come up with the same problem Sensei describes. Image #3 for this entry
http://www.rubberslug.com/member/gallery/item.aspx?id=283058
refuses to be deleted or replaced. I get messages indicating the image has been deleted when I try the "delete" button. But when the entry is selected again, the old image appears.
I have found that, once you try something ( a replacement of an image, entry of a new image, or deletion) and it does not take, you need to exit out of your web browser and restart it. Once things go wrong, they will continue to go wrong.
I know earlier that Jason said that RS was not supporting Safari on the Mac, just Firefox. My observations so far have been that new entries have the highest probability of working under WIndows 7. New entries work less often on Firefox on the Mac and much less often using Safari on the Mac. However, once a new entry has been created, the likelihood of an edit taking via either Firefox or Safari on the Mac goes up. Also, you need to watch text only updates. I have noticed that I get indications of successfully updating the text many times when I am not entering a new image, but the update doesn't actually happen. You need to exit the entry and then re-enter it to check that the text update took.
I'll restate my comment that error messages indicating that an entry is unsuccessful and the reason it is unsuccessful are really needed. That way we can at least eliminate the obvious when things go wrong, such as file names with too long a name or with unacceptable characters in the name.
I find that I can do the same thing over several times (of course, exiting the web browser & restarting each time) and, seeming at randon, have the entry take when it has been unsuccessful on previous attempts.
A final comment. When the automatic process does not generate a thumbnail, you can often create one manually and upload it. However, at times when that doesn't work, try entering a regular size image and then delete that image. Then upload image #1 again and let the automatic process do its thing. I can't guess why this would work, but it has twice now when all other ways of attempting to force a thumbnail in have been unsuccessful.
