Dear member of SanDisk Community, welcome.
Friend, is a problem of the card, it fails.
1- Please, clean the pins of the card, and device slot, with isopropyl alcohol (or if not, medicinal).
2- Test your card, SDHC of 16 GB, in a other laptops, directly to its port-card.
3- If still bad, in Start / My Computer , on the card icon, click the right mouse button, and then click in Properties/Tools/Error Checking and Repair.
4- If still bad, try formatting with (free): USB Flash SD Formatter 4.00, http://filecloud.io/jqtu1byc
5- If still bad, and gives _ write protected, _ is dead, return it.
6- If the above steps have not solved the problem, please back up your data, and contact SanDisk Technical Support, who will replace the device, if it’s authentic and within warranty.
SanDisk Technical Support: http://www.sandisk.com/about-sandisk/contact-us/
Regards, Alfred. (Google translated)