after I have made a selection with the marquee tool, or a path with the shape tool, when I hold down the space bar, it will not move the selection. I tried to move the selection with the hand tool as well, from what I understand it functions like the space bar?? Don't know.
There may well be other ways to move a selection, but I have always (after making the selection) used Select>Transform Selection. The cursor changes to the Move Tool and you can then move your selection.