I recently purchased a Seagate external hard drive. I did not set it up as the time machine automatic backup (I have another external drive for that) and I didn't set it up to use the Seagate software automatic backup utility. I just wanted it as an external drive on which I can dump files. It's connected by FW 400. If I unplug it, plug it back in, and restart the computer everthing looks find. But it disconnects when the iMac awakens from sleep. Any ideas what might be causing the problem?