Have since found out that the Zen app is not allowing a change of template AT ALL at this time. Have tried to change to the newly added and to other templates. No-go. So, am not sure what has gone wrong.
Next step, perhaps a new install of 1.3.7 (someone here said they got it to work) and updating that with multisite mod to see if it works any better... or? maybe trying 1.3.8.a again on a fresh folder.

G