Hi , I have a serious problem with flashing my Pipo S1 due to USB Unknown device issue. I'm running a Windows 8.1 64bit system and whatever I do I end up in the same problem. I have tried to install Win8 64bit drivers along with Windows7 64bit drivers but Windows always give the same lame excuse that the drivers I use can't be used. I have tried with official drivers from Pipo along with other links that people provided without any success at all. If anybody can give me a hint how to proceed I would be really happy. Otherwise I might give it try to flash it via my Linux(maya distro) computer. However I really saw that my Windows machine worked instead. I feel more much at home there .