Sounds like a dead or nearly-dead HDD. Leave it alone for some days, then use a cheap USB 2.0 enclosure and try to recover as much data as possible. In such cases i used the Finder first, to copy the entire drive contents to a different HDD. And if that did not work, i used Prosoft Data Rescue. I was not able to recover all data (approximately 75 percent recovered).I bought a G-Drive 500GB external hard-drive for my macbook, I have used around 200GB. It would generally work fine (although sometimes it would randomly disconnect) but now it won't connect to any device at all. Anyone know what to do?