Bidimensional dynamic array problem

[orgoton]

I have this

struct Vertex{
(...)
float z;
}

then:
Vertex vData[][];

Somewhere later:
vData.length=sizeX;
foreach(Vertex strip[]; vData[]) strip.length=sizeY;

Here the array is initialized. So far, I think I haven't done anything illegal. (SizeX and SizeY are runtime values, ushort vars). So first I say how many strips I want, and next, I put in how many elements that strip will have.

ulong m;
foreach (Vertex[] strip; vData)
{
      foreach (Vertex vertex; strip)
      {
           file.read(vertex.height);
           m++;
      }
}

Here I read the values from a file. First, I select a strip, and then go through all the elements of that array and read their values. "m" is a counter to see how many elements where read.

The thing is, m=0 at the end of the loop. What did I do wrong?