I have just bought a D5100 and a Sandisk Extreme 16GB SDHC card. I put the card in, formatted it and then over the next couple of days I got a "NO SD CARD INSERTED" error. It is an intermittent fault - I would pull it out, put it back in and it would work for a couple of shot but them the error would return. I returned the card and swapped it for a new Sandisk Extreme 16GB SDHC card but the same issue is still happening.
Is there something I am missing or is there an issue with the D5100 and these cards?
I am about to update the firmware - a new release on the 10/11 - to see if this helps but any help would be appreciated.