I just bought a portable WD My Passport 1 TB hard drive because I travel for business and I want to carry around some large data files (virtual machines) that don't fit on my Late 2008 model MBP's internal disk. I formatted it (mac journaled) just fine. The drive seems to work okay while I'm writing to it, but now, just a couple of minutes or less after I plug it in each time, it powers down and ejects itself (ie, is no longer listed in the Finder). I opened a terminal window and changed directory to the disk (so that it would appear busy since the shell has it in its current working directory) and then it won't power itself down but about every 60 seconds I get the following message: WD My Passport 0740 Media is in use and cannot be powered off. Try quitting applications and trying again. The messages stack up until acknowledged so I could potentially have hundreds to click through if I left it that way. Needless to say, this problem is causing the drive to be useless. I have a 2 TB WD USB hard drive at home that I use for Time Machine backups and I haven't had any problems with that one at all. I've left it plugged in for a couple days at a time while home. Is this a hardware problem with the HDD or a Snow Leopard OS problem? I need the space for a large work project and this is preventing me from moving forward. Thanks.