Hello, i understood what you mean exactly. I have FLX6 also and got same problem 2 times. I was using some kind of connector to extend USB cable and when i unplug it and use it with default USB cable only, there were no any problem. This is a BUS powered device so it may cause some problems if there are another USB connected devices which take power from your computer.
So i'm suggesting use the default cable only with no any additional cables or connectors.
