Time being 'frozen' is just a sort of shorthand really, it's only really a valid image if time is a strict progression from cause to effect, but as from a non-linear, non- subjective viewpoint, it's more like a big ball of wobbly-wobbly timey-wimey stuff,
then instead of time being stopped at one point on a line, it's more like someone's bundled the whole big ball up and stuffed it in a box, and everyone on Earth is in that box.
If you actually start thinking about the inconsistencies in the view of life in that box that we got in that episode, you'd go nuts, especially if you're a historian like me, so I find it easier to see it as a representation of that reality, a bit like the tube map is a representation of the reality of the Underground system.
Actually, what I'm finding most disturbing at the moment is that I watched it again last night with DD, who was out on Saturday night, and we both sniggered at exactly the same point, when the Doctor said 'River Song came twice'....