Originally posted by calsan How are you confirming the focus point?
The red LEDs you see in the viewfinder don't exactly match the real focus sensors - they're just an indication.
It could be you need to slightly move the camera to hit a focus point - not something you would notice if you were hand holding, rather than using a tripod.
My 5c about what could be happening, anyway.
and this assumes you were in spot focus too. if you were'nt that could be it. and you didn't mention the size of your model just that you were 3 feet away. if yur subject is very small, it might be too small for your cam to pic it up (though this doesn't explain why your wife's did... - maybe yours isn't defective buy your wife's is exceptional). need more info....