>I don't know why the vertical scroll bar of the grid doesn't work.
>I set the recordsource of the grid to a cursor which have only several record. Later, I set the recordsource to a cursor again when the cursor have many record.
>
>I can't use the vertical scroll bar to scroll down at the second time. Why? The scroll bar act like 'disabled'

I aso had that kind of behavior when I reassigned RecordSource. In my case it happened usually after 3-5 switches. I could not get any pattern in that.