Hi Patrick. Welcome to justanswer.
Does this error comes with all the lens?
Turn on the camera and while it is on, just Open the flash card door and when the door slides just push it back. This will reset the camera. Check if the error goes away or not.
Error is still present?
Do the reset once again as I instructed you to.
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Patrick there is some problem in the software of the camera because of which the error 99 came. It went away with the method that I advised but since the problem is still there, these small glitches are occurring. How old is your camera?
You can connect via usb cable but the software I am talking about is the firmware. And a fresh copy of firmware can only be installed by the Canon
You can try updating the firmware if its not the latest. You can download the firmware from this Link. CLICK HERE.
And if you can manage to click pictures by switching it off and on, then try doing that else you will need to take it to canon and they will install a fresh copy of firmware but you will be charged for the service.