I have a number of USB devices connected to my iMac either directly or through a powered 2.0 Hub. I have found that after restarting some devices have not started or found. I have to unplug the device from the hub and then re-plug or power off and on for it to be found. My Seagate 500Gb USB shuts completely off when the iMac is powered down which means I have to remove power plug and then reinsert. This totally drives me crazy. Does anyone elase have similar problems? I know I am new to Mac, but things like this are hair pulling.