Out of curiosity, is anyone experiencing this with a dual-band router when on the 5Ghz band?
I was experiencing this problem on my Surface Pro with my old DIR-655 Singleband n router. It turned out that it was my Bluetooth mouse that was interfering in some way, 'cause both the Wifi antenna and the Bluetooth antenna are on the same chip, and as both of those signals were operating in the 2.4GHz frequency, they were interfering.
Ever since I upgraded my router to a dual-band equipped router (the ASUS RT-AC66U), haven't experienced this problem again on my Surface Pro.