You contacted me directly about this, but I haven't heard back yet.
In case anyone else stumbles across this, so far the problem appears to be that the mame xml file never got generated at all. The xml file you attempted to attach and send to me was 0 bytes in length, so there isn't anything to work with.
In the next romlister update, I'll add a check to see if the -listxml command failed, and if so pop up some kind of warning box. I'm not exactly sure WHY that might fail, but that's our only lead so far... stay tuned mystery fans!