What am I doing wrong

I have been building access header forms with Subforms for over a decade now,
for some reason, in Access 2007 I get the following error
"The LinkMasterfields property setting has produced the following error:
"The Object Doesn't contain the Automation object "Section" when trying to
enter a new record into the subform.

(Section is the field in the parent table and the detail table that I have
tying the two tabels/forms together (Many sub-sections for a single section
identified by section, pretty basic stuff). What am I doing wrong?

Steve from Maine