I have a quick question and I thought someone could give me an answer to it. I have a Canon XTi camera with a 4gb Sandisk Extreme III memory card. I have noticed after taking a few pictures, 4 pictures or so, I am not able to take any more pictures for a few seconds because I get a "busy" signal. Why am I getting the busy signal? Is it from the XTi itself, the built in flash, or the memory card? Thanks.