"Lens not attached" warning when lens is in fact attached.

The Lensbaby Composer does not have any electrical contacts to tell your Nikon there is a lens attached. You need to put your camera in Manual mode and set the aperture, shutter and focus manually. Note that some cameras will not allow you to even shoot manually if there is not a compatible lens attached.

Hey there,
It sounds like your problem is related to the aperture setting on your lens. The aperture ring should be set to the smallest aperture usually f22 when attaching these older lens. Most lens aperture rings will provide a locking mechanism for that ring on the lens.
The aperture would be then set through the camera, not on the lens. Also some nikons have a lens preset on their menu, where you can inform the camera which lens is attached. Most of the older lens lack any terminal points for communicating with the camera automatically, therefore you will have to fill in the data manually to get better functionality out of the lens camera combo.

Remove the lens and clean the contacts on the lens and camera body where they meet with a cotton swab lightly dampened with rubbing alcohol.

When you turn the camera on do you hear the motor trying to extend the lens? if yes! get a can of compressed air and attach the included straw, give it a good two or three blasts where the crevice of the lens and body meet, at the same time press power to see if the lens housing can breaks free to extend. If this works point the lens down, and run the cycle three or four times to work any grit that might be trapped.

If it says lens error all you have to do is try pushing the lens back in. If that doesnt work, sorry! lol =(

I had the same thing happen to me and didn't use my camera for about two months. One day I decided to gently hit the side of the lens and the side of the camera closest to the lens as well. I still can't believe it, but my lens suddenly popped open and has been working fine ever since. Before this nothing had worked, including the gentle hitting of the side of the lens I had done before. I think I hit, or I should say thumped, the side of the lens a bit more forcefully this time. If your desperate, you might want to give it a try but make sure you keep thumping hit for a while before you give up. I think it dislodged some small particle that had been blocking the lens from opening up.

Did the only the lens drop or was the lens attached to the camera body? If the lens was attached to the camera, you need to verify that the problem is in fact the lens and not the camera body. The easiest way to do that is to try a different lens on your camera body or your lens on a different body. If you do not have access to either, I would find a local camera store that sells Nikon equipment. I am sure they will let you put your lens on one of there bodies. In any case, ff the damage is as extensive as it sounds from your brief description, you need to take it to a camera repair man. This is not a do-it-yourself job.

Ifd the camera is only 3 months old - return it for replacement

A lens error requires to be sent into repairs. Give them a call at 800-706-2534 option 2.

Error 99 is a general fatal error.
which includes the problems above mentioned by Q4SteveB but also many others.

It can be caused by a dicky shutter, problems with the CF card interface.

If cleaning and trying a different lens has not worked. Not definitive but as a rule of thumb...
If it letting you take one picture then giving error 99.. and the picture is saved to the card (but may just be black) this is most likely the shutter needs replacing..

If it takes a picture and gives error 99 but there is no picture on the card or the picture is 0KB its a CF interface problem.

If you get an error 99 when you plug in the USB its a USB interface error, you can try a different cable but unfortunately in most cases if another lens or cable wont work it needs repair