Mark Sanderson , Apr 15, 2010; 10:50 a.m.
Can you be more clear on where it says "busy"? Are you shooting in burst mode (multiple shots)?
Even then an 8gb card should be able to keep up in jpeg mode.
Try a new/different CF card. Make sure you format the card IN CAMERA and see if perhaps that helps. The card may have an issue or be corrupted slowing down the read/write speed.
Take it to a local camera store where the staff is more knowledgeable and can asses whether its working correctly or not. I doubt it has anything to do with the flash.
If they think there is an issue, I would insist BB send it for repair or contact Canon directly.