I'm not sure whether this is an issue with compiler or Phobos.
A testcase close to minimal:

import std.stdio;
import std.stream;

class S : Stream
{
	override size_t readBlock(void* buffer, size_t size)
	{
		(cast(ubyte*) buffer)[0 .. size] = 0;
		return size;
	}

	override size_t writeBlock(const void* buffer, size_t size)
	{
		writefln("%s", size);
		return size;
	}
	
	override ulong seek(long offset, SeekPos whence)
	{
		throw new SeekException("seek not implemented");
	}
}

void main()
{
	auto s = new S;
	writeln("created");
	ubyte[] z = [0, 1, 2, 3];
	auto w = s.write(z);
	writeln(w);
}

Saved as t1.d and compiled using command "dmd t1.d".

On windows 7 (64-bit) outputs:
D:\proj\d\utest6>t1
created
object.Error: Stack Overflow

On ubuntu 10.04 (32-bit) outputs:
epi@vbox:~/proj/xedisk/test$ ./t1
created
Segmentation fault