Photoshop :: Creating Icons In CS2. Halo

I have been creating icons for a 3D program for nearly two years now and used to send the icons in PSD format to developers. Just recently I have been sending the icons as BMP at their request but the icons now seem to have the halo effect creeping into them. They want BMP files and they use the upper left pixel of the icon to determine the transparency in the icon as they need a gradient background, and active state and the icons are desaturated when not used.

Anyway, here is the procedure I am trying to solve this but something is going wrong.

1. I use a 3D program to make 3D objects then render the image with a white background at 300x300 as a JPEG. No Antialiasing.

2. I open a new image in CS2, drag the rendered image into it then use the magic wand with antialiasing turned off? and tolerance of 30-40 to remove the white background.

3. Then I use Layers>matting>Defringe to remove any artefacts. At this point the icon looks fine.

4. I resize the image to 26x26 and choose Bicubic interpolation. Finally I drag it into a PSD document as a layer.

5. To get the image into a usable format I have a background layer of pink (RGB: 255,0,255) so that it can define the transparency then I save it as a 24bit BMP.

Problem is, when the developer puts it into the program it has a noticeable pink halo around it. I cannot do any more to remove antialiasing which he tells me is the problem.

Changing file format is not an option...has to be BMP?