I just hit what I suspect is a rather rare race condition. I have Banshee set to update and move files when metadata changes, and I noticed that if I set a large number of changes and then add the files to my HTC Hero. As the files in question were flac files these need to be transcoded.

However since Banshee returns directly after committing the changes to the database and the files are moved accordingly in the background, provided you immediately ask Banshee to transcode the files it will occasionally attempt to transcode files that have moved leading to errors and in one brave case a crash.

Reproduction:

1. Set Banshee to copy on import as well as updating and moving files according to the metadata.
2. add files in a format that isn't supported by your portable player and which have bad metadata
3. commit changes to metadata
4. after clicking okay, drag the files to your portable player

What happens:
Notice how occasionally Banshee will attempt to transcode non-existing files

Expected output:
After files have their metadata updated and related disk updates happened, the files should be transcoded and transfered to the device without errors.