My D5100 Nikon camera gives me the message no memory card inserted?

I have a sandisk 16 GB SDHC inserted correctly in the camera. I get the message "no memory card inserted". If I reset the camera, I have been able to get the SDHC card recognized by the camera. However, when I try to take pictures, it comes back with the same message "no memory card inserted". The sandisc 16GB is on the approved list to use in the camera. I have tried 2 different SD cards without success. These cards are working when I put them in my computer. Any suggestions?

Have you tried formatting the memory card? Right in the camera using the menu, or, if the camera refuses to do so, on a PC.