Hello. I have this annoying problem: OS Yosemite 27 inch Imac Late, 2013 I have 4 USB drives connected to the Mac via a self powered Belkin hub. During daily use (I never switch it off overnight), all USB drives are being ejected and remounted several times during the day, as I am working. I also get a message: "disk not ejected properly". Any ideas why this might be happening? Is this in any way harmful to the drives? Its been happening for almost one year now.