I have seen a couple of the issues you are describing in regards to not being able to update the order of the images or the descriptions. When I have seen this issue before it had to do with how the information was entered. What have you called your gallery and what are some of the image names that you have? Where you able to create the gallery and add images? If so at what point were you not able to add any more images?
The information that I have seen that causes these problems is usually cut and pasted from another text file, or special characters are used in the text. Please post back with any details you can about this so we can investigate further.