Help needed with ApplyUpdates.

[delphiman]

Can anyone tell me why ONE (below) works whilst TWO gives me the
following exception even though I have declared ChildrenDM in the
Uses Clause on DataModule ParentDM?

'Access violation at address 004CBE2C in module 'MDModel.exe'. Read of address 00000058'.
Process stopped. Use Step or Run to continue.'

ONE
On a TFormFather
procedure TfrmFather.btnUpdChildClick(Sender: TObject);
begin
ParentDM.IBdsTrnsfr.ApplyUpdates;
end;

TWO
On a DataModule ParentDM
with ParentDM.IBFatherDataSet do
begin
ChildrenDM.IBdsChild.ApplyUpdates;
end;


Thanks in advance.

Terry