D3S suddenly backfocuses (badly) with all my lenses. WTH?

I have 7 different nikkor lenses (14-24 24-70 70-200 105VR, etc...)

Both of my bodies (D700 and D3S) have always autofocused perfectly with all my lenses.

All of a sudden the D3S backfocuses BADLY with every single lens I own.

When I say badly I mean it focuses a good 10 cm behind the intended focus point, and that's at 1 meter subject-to-camera distance.

I have checked the camera's settings and AF fine tune is OFF, just like it has always been.

I have tried turning it on and using -20 values but it isn't enough to compensate...

I have also tried cleaning the lens mount contacts (but they were already clean before I started) and I have used an air blower to clean the AF sensor that sits below the mirror.

Also tried removing the battery for some hours and then putting it back on.

None of this helped.

Before I send it to nikon for repair, anyone has any suggestion of what else I might check?

Thanks in advance.