Thanks to darthanubis, I realized that I was hosting an out-of-date version of my Mythexport script. I’ve not used it in quite some time, since I no longer maintain a MythTv box. However, if some people are finding it to be useful, I’ll keep it around.
So, I hope this version works better for you.
Also, I guess someone decided to make a different Mythexport and include it in the Ubuntu repositories. After a bit a research it looks like this is a GSoC project. For the record: I am not affiliated with MythTV or Nuvexport. This is just a simple shell script that I wrote a long time ago. Sorry if I disappointed anyone.