Contents of formatted field vanishes when new data is entered into form

Hello all,

http://www.mihu.de/foo.odb

In my sample database "foo.odb" I have created a table "foo", with
fields "nr" (primary key, auto-increment) and "foo" (integer).

Then I added a query "sum_of_foo", which, well, calculates the sum of
field "foo".

Then I created a form "from". This has a table control which references
to table "foo". Next I created a subform below the main form and
connected it to "sum_of_foo". Then I added a formatted field and made it
display the "sum_of_foo".

Now when I open up the form, I can see the entries in the top and the
formatted field shows the sum of row "foo". When I change entries and
press "Enter", the sum is updated accordingly.

But, when you move the cursor to the row with the "Star" so that you can
add a new record, then the sum vanishes from the formatted field.

When you press "Enter" to confirm the new record, you can see that the
formatted field is updated , but the result is quickly erased again. If
you move the cursor away to an existing record, the sum vanished again.

Is this a bug or a feature? Did I do something wrong when setting up the
subform or the query?

You can download the sample database using the link mentioned above.

Best regards
Michael.