I don't think the problem is the drivers. it is the card. I have a Sony ultrabook with windows 8.1. This card never worked right, the wifi and bluetooth are were always erratic. this card is just not configured or made to have good reception, only works when is next to the router. I have installed a netgear usb wifi dongle and this and it works great. Your card is the problem, not the driver, not the computer, and definitely not win 8.1. You guys need to redesign the card, thoroughly test it and offer outraged consumers like me a replacement, instead of putting out low quality gear.
I suggest that anyone with the problem try a usb dongle, I guaranty that will not have the same problem. And that will prove that the card is no good..