When the stick arrives? Is it bought from ebay? That's why I said go to a shop and buy one, I have many ebay "branded" usb's here that won't flash a box.
Box don't know if its cable or sky during flash.
99.99999999% when a box wont flash it's either the wrong image or USB stick issue.
Maybe you can link to the image your trying to flash as you stated earlier its yours mates back up now its a TK one...can you link to the TK one so folks on here can help? More information the better.
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Also a tip I use that sucmnsee posted ages ago was when the flash complete and the box begins to boot, power off the box and remove the USB you used to flash the box and insert the one your going to use with the box and then power back on to save the USB used for flashing, so it remains fine to flash with, I do that every time and works first time every time.....I do leave it boot to over 30 on the LCD first before turning off and removing flash USB.