Ah ha! Found out what files Canola chokes on... I was writing a custom sync script since Canola can in theory play m4a and mp3 which make up the vast majority of my library, the DRM'ed tracks are automatically converted, cached, and then copied over.

Every single one of my iTunes plus tracks. They show up as file not found when I select them from a playlist and they do not show up under any other browsing mode.

If you want a few samples just send me an email address.

EDIT: Just because I know you will ask, it opens and plays just fine under "Media player".