I just checked in a new version, 1.0.1, which I have tested and found to be working with single image RSS feeds (specifically tested with the NASA feed you listed above). It should post to the site in the next 15 minutes, at which time you should be able to upgrade the plug-in from your WordPress install. Please let me know here if it gives you have any more trouble!
This could be caused by limitations at your hosting provider, but I'd like to see if it's something I can work around. Could you please open a new topic here with your issue? If you have time, I'd love to work with you on figuring out the cause of that problem so I can see about fixing it.