I was doing a portrait session with a 1 and 2 year old yesterday. When doing these sessions I usually just fire the shutter in continuous bursts. You can't really pose them, so I just try to capture the moments. Well I have a grip on my D90 and there were several times yesterday when I was trying to use the shutter button on the grip and nothing would happen. I don't know if it was making a poor connection or if the memory card was lagging. I usually don't have a problem with this but yesterday it happened twice causing me to miss a few opportunities. The grip is Nikon brand and the memory card is SanDisk 2 8g. Not the extreme or anything like that.