There is a utility you can run that might help pin down the problem. Start an administrative command window and type:
powercfg -energy
Watch where it puts the report before you close the window. There are other powercfg options, so perhaps type :
powercfg -help to see others in case anything else might help. There may be sleep options that would keep the USB hub awake, but I do not remember.
Operating System Win 7 x64
Computer Type Homebuilt
OS Service Pack 2
DirectX Version 11
CPU Type and Speed i7 3770K
Motherboard Chipset Asus P8Z77-V Pro
System Memory Type 16 GB Kingston
Video Card Type and Speed Nvidia GTX 680 (2)
Computer Monitor LG 27" (3)
Hard Drive Kingston 240 SSD
Optical Drives LG WH12LS30 Blu-
Modem-Router Type Linksys E3000
Network Adapter Intel Gigabit
Anti-virus Software MSE
Computer Skill Level Average Ability
Windows Experience Index 7.7