Reinstalling ogg-support got me back to where I was. Should have thought of that myself, thank you.

I've installed decoders-support, but get the same result.
One odd thing now is that one album has appeared in the list of albums for one particular artist, and the list says it has 3 songs (which it does, it's an EP), but when I go in it says there's one song, no details for it.

I'll have some time later to try again.

Thanks for the help so far.