I just purchased a Plugable 10-port USB 2.0 hub for my laptop. I have a mouse, a dongle, an external USB 2.0 drive (Western Digital) and an M-Audio interface (Fast Track Pro) connected, and the hub is hooked up to its own AC adapter.
When the computer sleeps or is turned off, the USB hub starts beeping, and continues to do so until I disconnect the hub from the computer. The beeping happens even with no devices attached to the hub. When I disconnect the ac to the hub, the beeping stops, but then the WD drive clicks and sputters, like it’s not getting enough power, and the laptop does not recognize the drive.