I have same kind a problem:
I can see the card (8GB micro SDHC Kingston) in windows explorer, but when I plug the card into N810 it does not read it. Previously I have used diffrnt. brand card. N810 did read it for couple of times. After 2-3 times of putting in/out the card started to not showing up. I thought the problem is in card and I bought Kingston one, but the kingston did not work too.

**********Can you help please, is there any way to put drivers or somehow recognize micro card.