I have the nikon d600. I take a lot of pictures of kids and therefore need to take multiple picture sequences. Usually after 4/5 quick pictures, I hit the button to take and it pushes all the way down but won't take a picture for 10-15 seconds. I use to have the nikon d90 and never had this problem. I don't know if my cards are too slow or if it can't keep up with the sequences, but it is so frustrating. I don't know what to have looked at? At first I thought it couldn't find a focus but this occurs even when i don't change position after multiple photos and I miss a lot of moments. What would cause it to free up or not take a photo?