Canon USA have confirmed that: "images captured by continuous shooting, and under certain conditions, barely noticeable traces of the immediately preceding frame may be visible." As a result, Canon are analysing the cause of the problem, and will release firmware to to address this issue.
Canon say this problem is not noticeable when optimal exposure is used and it may become more noticeable if retouching is used to emphasis the image.
"We offer our most sincere apologies to customers using this product who have been inconvenienced by this issue," said Canon in their service notice. "Going forward, we will spare no effort in our quality management to make sure our customers can use our products with confidence. We hope our efforts will earn your understanding."
ePHOTOzine have contacted Canon UK for their response.