I've been back and forth with Intel for six weeks but nothing useful has come of it. First they asked all the obvious things I'd already tried. Then they sent me a link to older driver version 17.0.6_e164, but I couldn't install it because it thinks the Windows 8.1 default driver 16.0.0.62 is newer and refuses to install over it. If I uninstall the wifi card's driver, Windows immediately reinstalls 16.0.0.62 and I haven't found a way to prevent it. At least I tried.
Last I heard from them, Intel wanted to know when they could give me a call, presumably to walk through all the stupid obvious things again and waste my time. My last two emails to them bounced so I guess I won't find out.
The only thing I can say is that the issue only occurs on some wifi routers (mine is a D-Link DIR-655), so you might try replacing yours if you can.