Some people are reporting a weird bug in Nikon Capture NX software. Enter a small value for the exposure compensation (e.g. 0.01) and the photo becomes less sharp. I had trouble reproducing this bug on my own using Capture NX 1.3 and NEF from my D200. So it appeared to be related to specific circumstances.

I then downloaded a D300 NEF file and to my surprise, it happened! I also found that if you change the exposure compensation in Raw Adjustment, you will no longer be able to change the sharpening setting in the Picture Control: dragging the sharpening slider will have no effect. If you do not perform the exposure compensation adjustment, you can adjust the sharpening level using the sharpening slider in Picture Control. As soon as you do any exposure adjustment, the sharpening will disappear. You can get the sharpening back by unchecking the Apply checkbox next to Exposure Compensation.

I think this is related to the Picture Control system in the D300. According to Nikon, the unique Picture Control system makes it possible to share image processing settings among compatible devices and software. It is likely that there is a bug in Capture NX related to the Picture Control. Nikon D200 does not have Picture Control system and is therefore not typically affected. However if you turn on the Picture Control on a NEF file from D200, you can experience the same bug! It doesn’t seem possible to turn off the Picture Control for NEF files from a D300.