I did a little investigation (what little I can as a non-Roku guy), and here's what I've determined.
It looks as though, for whatever reason, when SoundBridge tries to fetch the data for any track in the library, it gets data for one specific song (i.e. no matter what song you try to get data for, you get this one song).
This has two side effects:
1) If the song whose data you get is of the same format as the one you're trying to play, then the track will play, but the displayed information will be incorrect.
2) If the song whose data you get is in a different format (different codec), then the track will fail to play, because the SoundBridge is trying to use the wrong codec.
I've passed this info along to some friends at Apple, and I'm sure Roku will be reporting the issue directly as well.
This could be an iTunes bug, or it could be that a change in iTunes has revealed a latent SoundBridge bug. As Roku and Apple investigate, I'm sure we'll find out which it is...
Hope this sheds a little light.
Formerly "RokuMike", but these opinions are mine alone.