First a hint: if some SCC operation fails (like in my case mppdec) and remains as a zombie, you will not be able to start mt-daapd again (port 3689 still in use).
In that case, see if port 3689 is still open (e.g. CLOSE_WAIT):
netstat -an | grep 3689
Then see which process has it opened:
fuser -n 3689
And terminate that with the [id] fuser returned:
Now to the actual problem, from a -d9 dump:
Executing: SELECT * FROM songs WHERE ((((genre like ‘%
Could not start enum
Same song database that ran with the november nightly just a few minutes earlier.