FD to EF adapter confusion

[y75stingray]

I recently bought a Fotodiox brand FD to EF lens adapter for my 5dMII and 1DS. I can get it to work without any trouble on the 5DMII but all it does on the 1DS is lock the mirror up. does anyone know why this would be? do I have to change a setting on the 1DS? It states on fotodiox website that the adapter workss for both models. Any help would be appreiciated!!

 

[Big Mike]

How far does the adapter extend back into the camera? It could be interfering with the mirror's travel.

 

[y75stingray]

It appears to be identical to a EF fitting and i dont see any sign of any contact but its tough to tell since i cannot view it with the lens attached.