The Nikon D100 manual does not endorse or reccomend the use of NiCd or NiMh batteries, only the alkaline AA's-which may or not perform properly. This problem is (hopefully) being addressed by Nikon thanks to the thread Victor and I posted. I have not had any feedback from Nikon since Sept. At present, without much testing the Duracell Ultra AA's MX1500 appear to function. They have an 80 milliohm internal impedance as compared to >250 mOhm impedance of the MN1500 or other? quality AA's. This techn-babble simply states that the voltage drop at the batery terminal is a lot less, tech support indicates that the microprocessor in the camera checks the battery voltage every time a function is activated (autofocus, shutter release, flash,etc), if the voltage is too low you get the Err message and the camera 'hangs up' preventing further malfunctions. Removing the AA holder and reinserting the EN-EL3 resets the systm and you can continue.
I am surprised that the NiMh got off even 1-2 shots, try the MX1500's; let me know how they perform.