The err99 could come from a lens incompatibility, a battery problem, a shutter problem or just "dirty" contacts on the body/lens contacts

does the problem always occur ?

i reccomend reading this

An Error99 could be anything, absolutely anything could have gone wrong with it.

Does it always show Error 99? or does it only show Error 99 every now and then? Is it when you do something specific?

Try switching your CF card, battery, and lens and see if that helps

Any EF or EF-S lens should do and any CF card should work

Batteries on the other hand should be genuine Canon battery or a reputable generic brand.

If this does not work, contact Canon and they will tell you the closest repair facility you can send it to to have it checked out.

An error 99 is not anything, but is an undefined error that's not described by one of the documented error codes. That's been standard for decades. I always start with the quick-and-easy stuff. A soft pencil eraser to clean contacts on lens and body, and the battery. Visual check of memory card and compressed air to clean contacts of dirt.

Similarly, my flash gave an error, and compressed air cleaned the sensor arm in the tiny hole below it, and all was well. Use low pressure and be careful. Use extra light for a good visual inspection.

i also have this error 99, on my canon 300d and have tried all the above, fully charging battery, cleaning lens....then then shutter still got stuck, im at a loss, and cant afford to replace or send away for repair, is there any thing else i can try ? i hate being with out my camera

Error 99 is a generic call for help. 95% of the time it is a failure in the shutter. It can also be a lens problem or flash problem.

Error 99 showed on my EOS350d when the body could not set the desired aperture in the lens.

This occurred on my old Sigma70-300 (1999) on anything except wide open and was due to the lens being old and 'not compatible' with the newer body. I was able to take the lens to the Sigma repair agent and have it re-chipped to compatible firmware. The lens worked perfectly since including on my new 550d.

Error 99 showed up on my 350D when the aperture of the kit lens got stuck fully open. The camera could no longer adjust the aperture so trying to set it to anything other than f3.5 resulted in this error. Since this was the kit lens, my solution was to buy a replacement lens.

For me cleaning the body contacts (firmly) worked well.

I also tookout the little memory battery(next to the main battery/or battery grip insert) and placed it back.

But i think cleaning was the solving of the error 99 problem.

error 99 common problem on camera REBEL XS

problem is on main board, replacing main board will fix problem

other problem on main board is : did not read memory,stuck in one langue - can't change langue . Good luck Neb

I just got an error code 99 on my camera and when I took it into the camera shop in town it was my shutter that was flexing. I have to send it off for repairs. I have no idea how much it is going to cost.

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.

If the “ERR 99′ message only appears when one particular lens is

attached, then that lens should be examined by a service technician.

If you see the “ERR 99′ with a different Canon lens attached, then the

camera should be serviced.

http://www.fixya.com/support/t182551-err...