I've similar experiences when exchanging mini-pci cards. The original would connect through walls and on different floors whereas the new one only worked when next to the WiFi Router. I tried various forums, including one specific to the make, and found others had simialr problems. It seemed to be a random event and difficult to spot in advance. The final advice was always 'return the card for a refund and buy another make'. I went back to the original card and had a refund.