Having Same issue on my D54250WYK NUC, got the 7260HMW today, the Wireless is working but the Bluetooth Keeps showing error Code 43 with driver version 3.1.1309 or Security descriptor error with driver version 3.1.1311. with Windows 8.1 Pro x64 as well.
@Maibad31 can you remember what driver were you using when it did work. what did you when you installed it that it worked. Have you installed something lately maybe this is what is causing the card to not work on my NUC as well.
Thanks