I have a 3 year old 200GB AcomData external HD. I use it everyday at work with my mac pro tower running 10.5.5. It has always worked like a champ. Yesterday afternoon I went to open up a file and it gave me a warning that the file was not recognizable. It was a file I open almost every day. I tried a newer file and it gave me the same warning. I tried to eject it but it wouldn't let me. So I shut down my computer and disconnected it. I restarted my machine. Once it was up, I connected my external again (using firewire as usual) and the screen went black from top to bottom and a waring came up saying, "Hold down the power key for several seconds to shut down your computer". I tried it on another mac at work and got the same results, and again on my tower and laptop at home. I have about 150GB backed up on other hard drives but desperately need that other 50GB. Any suggestions? Oh, I also tried all of the ports on the back and tried using a different firewire cable. No luck. Thanks.