Error 99 I have a 75-300mm zoom that i used with my 300v and it works perfectly. Now i have a 400d, often when i take pics error99 appears on the camera. It does take pics but not the settings that i want, the pic is too bright. How can i sort this out?

The possibilities are.. 1)the lens doesn't fit with 400D, i hv experienced it.I use a lens on my friends camera,it turn out find,but on my camera, it says error99. 2)Maybe the lens is broken,maybe the aperture wire.

I had the same problem and i found this guide online fixed my problem

1. Turn off the camera.
2. Remove the lens, battery, and CF card.
3. Allow the camera to sit without power for approximately 20 minutes.
4. Insert a fully charged battery, and turn on the camera.
5. Depress the shutter button as you would to take a picture.
Does the “ERR 99′ message appear? If it does, then the camera should be
serviced. If it does not, then please proceed to the next set of steps:
1. Turn off the camera.
2. Insert the CF card.
3. Turn on the camera.
4. Format the CF card in the camera.
5. Depress the shutter button as you would to take a picture.
Does the “ERR 99′ message appear? If so, then the CF card is the most
likely source of the issue. Try using a different card.
If the message does not appear, please complete the following steps:
1. Turn off the camera.
2. Clean the lens contacts by gently rubbing them with a pencil eraser
or soft cloth. Be careful that you do not let any debris fall into the
camera body.
3. Reattach your lens.
4. Turn on the camera.
5. Depress the shutter button as you would to take a picture.