I have had my new iMac 21.5" for about 2 weeks now. Yesterday I picked up a 500 GB LaCie USB Drive to be used for my Time Machine drive. I have the drive connected directly to a usb port on the iMac. Sometimes when the iMac goes to sleep, when I wake up the iMac I get the dreaded "This Drive Has Not Been Disconnected Properly" warning. I have made sure that the "Put Hard Disk(s) to Sleep Whenever Possible" option is not selected under the Energy Preferences. I have tried multiple usb ports, same issue. This isn't a constant issue, it just happens sometimes. Any thoughts? Is there anyway to tell Time Machine to mount and unmount my drive when needed? Thank you MR for your help!