Ok I'm stuck in the cam shop wondering to get a batt grip or 35mm f/1.8 and I'm able to get either one of it... What do u guys think? I'm on a tight budget recently =(

How durable D90 is to weather?

Hmmm...thinking wanna got Nikon BTS to try a few lens and poison myself  

or maybe to send my camera for service

if u think like that.. what else option u got? get a DX camera loh 

24-70mm with D700? 
That's WAY out of my budget. 

Out of budget too. Only got 8k. 
Is D7000+Siggy 17-50 f2.8+50 1.4D good enough you think? 

lol..so early 2 hav problem meh..  

Ya sigma got that issue , that y i choose nikkor 50mm 1.4g , better accuracy focus

If u get nikkor sure will not get back focus problem..lol

Try unmount and remount the lens. Try shooting with tripod using timer, is it really have back/front focus now?
Let some experienced DSLR user try.

using small aperture is harder to tell back/front focus because the depth of field is covered more.

Are you shooting in low light?
Are you using external flash? If yes, is the flash AF assist lamp turned on?
If no flash, is the on camera AF Assist lamp turned on?

When the focus is locking on, is it lock-on instantly or does it judder a little while locking on?

Did the AF assist lamp fired? Try turn off the AF Assit lamp and try again?

At aperture f/1.4, slight movement (not noticeable) will also move the focus depth/plane. The DOF is very shallow, and also depend on your distance.
16-85 have smaller aperture.

Try shooting at f/2 or f/2.8? Shoot closer to your subject and re-check. If you have a Nikon DSLR friend, try mount the lens on his/her camera and you try it then let your friend try it.

^ If you talking about far subject it back focus right?

That one are you using your center AF? or using the sides?

True, I think it depends on the person, but for people who are not used to wide aperture especially first timers or new to DSLR, it's critical. In other forums, you'll find many complain about front/back focus, when most of the time, it's because of the slight movement or how they hold and snap photo, it's like not Point and Shoot, which is really point and shoot; With DSLR, you need to hold it more properly and also when pressing and after pressing the shutter. Some people, moved the camera during or RIGHT after pressing the shutter which can caused OOF images or shift the focus plane/depth.

Of course, I'm not trying to deny the problems, but to help people to identify first.
But previously you tested there is no such problem? It the lens dirty? etc?

I'm not sure if a lens can have front/back focus issue overtime, if yes, then everytime need to send back for adjustment/tuning? Or something happened?

Use AF/AE Lock button, or configure the half-press shutter to lock both focus and exposure.
Yes, you can use that or configure the settings, for both the AF/AE Lock button as well as the half-press shutter.

If you're using the AF/AE lock button, default for D7000 I think is lock both Focus and Exposure, so if you hold it, the focus and exposure will be lock until you release. So even you release the shutter, it's still maintained,

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Added on February 1, 2011, 12:25 pm

Since the SC is close, nothing much you can do. Try to check for finger prints/etc on the lens, clean the lens and re-try. If you have other friend with other Nikon models, no harm to try it out since you can't send to SC anyway now.

Good Luck bro; Sorry to hear about the bad news.