Err99 on my Canon EOS 350D

So I was out shooting a football match with my Canon EOS 350D, and after I changed my lens to the 75mm to 300mm telephoto lens, each time I press the shutter, an error 99 will be displayed. I tried to clean the contacts on my lens and also on my camera, and they seem to be very clean, but that doesn't solve the problem. Then I tried to shoot at f/4 and it seems to work. It works at f/4, and that's it, all the other apertures will display err99. So what problem is this? What should I do? ( I tried on other lens and cf cards and it works fine so I guess it’s something to do with the lens)