I was fiddling last night with my D300 and 17-55mm f2.8. I didn’t think it was the sharpest copy I had ever scene. I used the AF fine tune to reset the lens back to 0 as the previous owner of my D300 had set it to +20.. Some pics from this evening after work.
This intense stare is from watching Pingu on the TV!!
Time to play with some cars..
Try on dads top..
Happier with the lens now, after the tweaking..
adam mcateer photo blog 
I’m still not sure about that lens or could it be the D300…try the brick wall test.