This doesn't work:
    if (format->id == WINED3DFMT_DXT5)
    {
        if (target == GL_TEXTURE_3D)
        {
            struct wined3d_format throw_away;

            texture->resource.format_flags &= !WINED3DFMT_FLAG_BLOCKS;
            throw_away.upload = format->upload;
            format = wined3d_get_format(gl_info, WINED3DFMT_B8G8R8A8_UNORM, WINED3DUSAGE_TEXTURE);
            f = *format;
            f.conv_byte_count = 4;
            f.upload = throw_away.upload;
            format = &f;
        }
        else
        {
            f = *format;
            f.upload = NULL;
            format = &f;
        }
    }

This does:

    if (format->id == WINED3DFMT_DXT5)
    {
        if (target == GL_TEXTURE_3D)
        {
            struct wined3d_format temp;

            f = *format;
            temp.upload = f.upload;
            format = &f;
            format = wined3d_get_format(gl_info, WINED3DFMT_B8G8R8A8_UNORM, WINED3DUSAGE_TEXTURE);
            f = *format;
            f.upload = temp.upload;
            f.conv_byte_count = 4;
            format = &f;
            texture->resource.format_flags &= ~WINED3DFMT_FLAG_BLOCKS;
        }
        else
        {
            f = *format;
            f.upload = NULL;
            format = &f;
        }

    }