> The offending line is IBODataset Line 7553:
> else
> if ACol.IsNull or ( ACol.Value <> AParam.Value ) then

----->> ACol.Value := AParam.Value;

> end;

> In this case I have an ACol.Value = 42 and an AParam.Value = ''

I hit something very similar to this recently (but not in IBO
code), I think it relates to changes in newer Delphi variant
processing. (#!&^*% ... I cant remember the details, just
that a section of code started to throw what seemed to be blank
string errors that did not happen in Delphi 6.)

Step down another level to:
procedure TIB_Column.SetAsVariant( const NewValue: Variant );

to try to see what is happening in more detail.

That is; if AParam.Value really is a string value that cannot
be converted to double (whether it is '' or 'xxx') then we
need to find out why that is happening. If this is the case
you need to look back to where AParam is coming from and see
if you can tell where the string value is being assigned.

However if AParam is null or is empty then the code in
SetAsVariant is supposed to detect this situation and set the
column to null.

Need to work out (for certain) which situation you are facing
before taking it much further.

--
Geoff Worboys
Telesis Computing