How can I prevent Impress in Slide Sorter view from showing just one large slide?

Slide Sorter view has stopped working correctly for some .odp files in Impress 4.4.5. It shows only one big slide – thus making Sorter view useless for rearranging or inspecting many slides. Zoom menu is faded out completely. There seems to be no relevant Tools > Option to set default zoom in Sorter view.

Make sure menu View > Toolbars > Slide View is enabled. This toolbar has the field “Slides Per Row” to set arrangement of the slides. The zoom is set automatically according the width of the window.