gameranand
Living to Play
Well actually the thing is that you are basically drawing power from 1 USB port and distributing them in 7 parts. Now when you connect one device then its alright because you are basically just routing the power but when you connect 2 or more than 2 devices which requires good amount of power then the devices won't get necessary power and Windows will fail to recognize them so 1 device at a time. 
BTW where you have connected this USB hub ?? In back I/O ports or the headers of your mobo ??
BTW where you have connected this USB hub ?? In back I/O ports or the headers of your mobo ??