A simple USB cable to Seriel (FTDI) loses from Port 7 repeatedly the connection (LED on the hub goes out and the data can not be transferred). The cable works flawlessly directly on the computer and to port 5 and 6 and in addition to the converter chip in the cable and no current is drawn. No stable connection at all ports -> unusable.
Btw. As already mentioned, the included USB cable is quite short.