105mm Macro VR f/2.8 Aperture problems. Help please?

I have 4 lenses and use a D2x. If I use my 105mm f/2.8 VR Macro in aperture priority mode, I believe you should

be able to use the main command wheel to choose an aperture between (in this case) f/2.8 and f/32. When focusing

on a subject say 10 feet away there is no problem and I have the full adjustment from 2.8 to 32 However, when

using the lens close up as a macro I can only achieve a max aperture of f/3 but also a bizzare minimum aperture

of f/51 (yes fifty one!!). Is the lens faulty or the camera or more likely something fundamental that I don't

understand about macro lenses!!?

All my other lenses seem to behave as expected even using them as close as I can go to the subject.

This is normal for macro lenses. There's numerous discussions around here that talk but it.

We just discussed this yesterday:

http://www.photo.net/nikon-camera-forum/00QU5K