New Sigma 17-50 2.8 OS on D5100 problem

Thank you uncleskull for prompt help. I have tried focusing on all sort of subjects , more on high contrast subjects because I knew that subjects with low contrast are tough to auto-focus.. Tried with OS on and off, at near objects and far. Manual focus works fine. Tried cleaning contacts on camera body as well.

I have five other lenses with no problems. Have owned Sigma 17-70 OS previously though soft wide open at FL longer than 35 mm, autofocus was never an issue, fast and accurate.

I use single point AF-S mode. The behavior of lens is same in broad daylight and indoor except that hunting is a bit longer indoor. All images appear extremely blurry like this one 100% crop , I tried focusing on building in the center.