Chris,
As you say, anything more that 5M needs an active extender. Last night I had some success .. well it all worked for 6 hours but then lost the will to live. Although it would then re-connect in PHD2 and even show in Device Manager (Win8.1), the GP refused to capture images. I gave up at that point!
As of last night only one end of the extender cable was connected to a "high power" (1A vs 500 mA) usb port, I've just added a second powered hub the other end of the 10M cable - maybe it is just a power thing - which again goes back to why on earth doesn't the GP work off the One's USB port. Most annoying.
Anyway for this morning, as a test, I've fired up PHD2 and Sequence Generator Pro and got them both capturing and I'll see if the extra powered hub helps.
and I bought the One 6 kit to simplify my setup .... doh