My Lion always try to disconnect my external hard drive when I was watching movie from my external hard drive or copying large files to it. It's about 20 minutes after I connected it to my macbook pro and I will got an alert every one or several minutes after the first alert. It says "WD My Passport 0740 Media is in use and cannot be powered off." I have closed the auto-sleeping after a long idle time using the WD SmartWare. Could someone tell my what's the problem? I am really confused by it. And the same problem happened when i was using a usb hub. My macbook pro disconnected the usb hub every several minutes and then auto reconnect it. All my usb disks or flash card were removed and then auto mounted.