Norie is exactly correct.
I'll try to explain a little. I'm guessing that what you're doing is referencing the recordset in your tabular form using something like Me.fieldname1.
What this does is only update the contents of the field in the currently selected record. If that record is always the first one, then that's probably why you're only seeing the first getting updated. This would also be the case if you never actually selected anything within the table...it would default to the first record.
If you allow edits to the tabular data, set up an UPDATE query that checks the contents of the entire recordsource for a True value in the displayed check box. You then should make sure that you refresh the recordsource so that it updates the display (and by your description, removes the checked items from the tabular display.
Mike