Sorry I haven't used MoonShell since 2009 and have no experience with converting Youtube clips to DPG.
Your problem sounds like it comes from an issue with the dpg converter software and not MoonShell so this update won't help you there.

In reply to your edit: Yeah, I've been away from the scene for ages

This post has been edited by Triforce, Thu, May 17th, 2012 at 17:22