the same thing just happened to me too. I removed my sandisk 6GB microsd with microsd adapter from the n810 then put it into the usb card reader on my PC. I put it back into the the n810 and then it won't boot. the blue bar gets to 100% and it just hangs. I remove the card and it boots fine. I was using this card for 3 months with no problem. If i put the card in after the device boots, the n810 says the card is corrupted or not formatted. I proceed to format and still have a problem....I'm going to send the card back for warranty repair unless anyone has a solution? p.s- the card seems to work fine in my camera and my win xp pc via usb.