I've had my D4 since April...went right to work with it and shot 16,000 images first weekend. Since then maybe 25.000 more; inside gym venues, outside football field venues and even a sailboat race while riding in one of the competitors. All settings have been consistent with minor iso variations. Last Sunday was shooting an outdoor activity, hooked to the 200-400 f4, and suddenly she wouldn't fire. Tried re-mounting the lens and that seemed to work, but only for a minute or two...same problem. Switched to my 70-200 VR and got the same problem...even with my 24-70. Condition is intermittent, re-boot camera, battery out/in, cards seated and reseated. Lucky I had my D800 to backup (man, it's SLOW...hahahaha...but good)...so, anyone ever experience this condition? No matter what, it's in to Nikon after the holiday, but maybe someone has some info/advice?