Hey Kris,
Sorry to hear the export feature isn't working for you. Spriteme isn't under active development right now, so if you'd like to see the bug fixed right away, you're totally welcome to grab the source and dig in yourself. You can send a fix patch to this google group or submit it via the SpriteMe googlecode site.
Steve may have some extra cycles to hack on this--if so he'll probably jump into this thread.
I hope SpriteMe was still able to help you build sprites and speed up your site :-)
Take care,