My 70-200 is acting up. When mounted and shooting,

SOURCE: My Nikon D300 doesn't recognize the 55-200 AF-S DX as a cpu lens.

you call the computer expert to your home and then tell him this thing. he will give you the full idea about it. from my side it is the camera body.

SOURCE: I think I messed something up on my lens.

You are correct that the switch locks the aperture. In order for your camera to function correctly in the auto-focus mode you must lock the aperture to the smallest opening (largest number such as f22). The switch has two positions. The position where the switch is lined up with the orange line is the locked position. When the lens functions properly and on the camera, the lens aperture is forced wide open by a pin on the camera body pushing a lever on the lens that opens the aperture. As part of the sequence when you push the shutter button, the camera releases its pressure on the spring-loaded lever on the lens, allowing the aperture to close to the setting that the "computer" has determined as correct. You will find this lever on the outside of the black ring that surrounds the rear lens element. With the lens removed, find the lever and make sure that with the lens set to the f22, sliding the lever counter-clockwise against the slight spring tension, the aperture opens wide and returns to f22 when released. If this is not the case, the problem is in the lens. If this works, then the problem is either in your camera body or in the alignment between the body and lens. If this does not get you on the right track, let me know what you find and we will proceed from there.

SOURCE: Lens mount plastic is broken on Lens

Unfortunately your lens is one of the kit versions which were built as cheaply as possible with a plastic lens mount. They were never intended to be repaired, but to be fair they usually seem to last quite well on the 18-55mm versions but the 18-105mm is heavier and longer and I've found that the plastic mount is particularly intolerant to any handling errors on this lens.

A professional repair will normally cost more than the lens is worth, but you can sometimes buy new replacement mounts.

Use your favourite search engine to look for part number 1C999-488. Unfortunately they're rarely in stock whenever I've needed one. You may also want to search for a scrap lens with a good mount which you can replace yours with, but scrap lenses of the correct type usually have faulty or badly worn plastic mounts as well.

Carefully assess your lens before making the repair: unless it's in perfect working order in all respects except for the broken mount then you'll be better off buying a new or used complete replacement lens.

SOURCE: Problem with new D90 and old Nikkor 18-200 VR lens

Try a diff lens on the D90 to see if its the body or the lens. Tony

SOURCE: Nikkor Lens Cannot Manual Focus

It sounds like you had the lens set for manual focus when you took the A / M switch plate off. If this was the case then when you but it back together the little arm behind the plate is on the wrong side of a moving gear assembly.

To fix, remove the auto/manual focus switch plate from the camera (just the one screw not the ribbon beneath) Push the switch over to A. Hook the bottom of the plate back to the lens and put the screw back in. Done!