Grid issue with smDisjunctrow

I have a grid, where the selectionmode is set to smDisjunctrow. That works fine. But when I disable the selectionmode via code with smNone, and set it back to smDisjuctrow, and then click somehwere outside a cell in the grid, so that the grid get the focus, just a single cell is selected, not the whole row, even the selectionode is set to smDisjunctrow.

Did you wrap the code with BeginUpdate / EndUpdate?