Default values != new record

I have a v3 form with a master-detail setup. One field of the detail is populated directly with $$date$$ as default and another is populated with a default value via a pre-block trigger selecting a value into a control field and thence into the detail field via its' default value.

The problem is unless I add something into one of the remaining fields (or change one of the defaults) Oracle doesn't think there's a new record there at all - I get "...no changes to commit." The doc says otherwise.

I have the sneaking suspicion that I'm missing something *real* obvious but for the life of me I can't see it. Can someone put me out of my misery please.

(I've mucked about with on-new-record and key-nxtblk [on the master] but, alas, no joy.)

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M