Glass problems. BIG glass problems.

[venchka]

Originally Posted by wildhorserunphotography

I may try to tighten it myself. Thank you for the tip!

I've used this lens on both my d200 and d300 and it's definitely the lens that's messed up. I checked the focus points as well.

I'll keep you posted!

If it's the mount, and I doubt it, you still need to get it properly repaied under warranty.
Since the focus problem moves with the focal length, my vote goes to internal allignment OR an element that isn't shifting properly to alter the focal length. Regardless, it needs to go in for repair.

IF...the repairs are not covered by warranty, then you need to weigh the cost of repairs vs. the cost of a replacement lens.