I see what you mean.
On my XP system, I selected the show grid option and found that I could not drag an object to position it between the grid lines unless I held down the Alt key while dragging. Minor grid steps where set to 1, Major to 6 and objects appeared to snap to the major lines even with snap turned off. If I increased the major and minor grid intervals, however, I could then drag to positions between the major grid lines--suggesting that there is some minimum increment to which you can drag unless you hold down a modifier key. I also found that if I zoomed in, I could drag to smaller grid increments.
I don't know if this is a bug or "by design".
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