Yep, there’s a file missing in the NSLU2-arm-ipk-file: the config.xml from the admin-root did not make it into the package and without it, the config page is not built up correctly.
Just grab the sources and copy the config.xml from the admin-root-directory to the correct place on your slug (probably /opt/share/mt-daapd/admin-root) and make sure that it is readable by the user under which mt-daapd runs.
This should do the trick, at least it did for me.
@Ron: Maybe you can look into this for the next nightlies – somehow this ‘config.xml’ got lost on the way…
Have fun,
all the best,
Nico