that's not it...
Edit your Site definition in Dreamweaver and Change the "Create Links Relative To" option on the Local Info tab to "Document" before running the DataAssist wizard.
Thanks for the reply, but I had seen this advice in the past and noted in my OP that 'links relative to' was set to 'document.'
I did work it out, sort of. After a number of efforts failed, I finally another user on my PC, reloaded the DA extension there, and now have managed to complete the wizard again. If only I could recall how I had fixed this before in my detail page:
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