Hi, I am using a nikon d7000. I noticed that after 5 shots, the shutter is disabled for sometime till i can start taking pictures again. The green led at the back is constantly on when the shutter is disabled. I am using RAW lossless but when i change to jpeg, it works fine without any problems. I think that the buffer is exhausted and photos are being written on the card. I am using sandisk 16 gb class 4 cards in both slots with card 2 in backup mode. Should i buy the class 6 card if that is the problem?