I have a MacBook air (2011 aug model) with lion and my wd my passport 2tb won't unmount. I've tried adding partition, force unmount lsof | egrep 'name of drive' the way described on here(but I think that's for snow lep), and I downloaded disk warrior but it still says it can't unmount because another application is using it. I'm sure it's corrupted somewhere in it but if I could just get it to unmount I believe disk warrior can rebuild it. I have been able to erase it so I don't need any files off of it. Is there a different force unmount procedure to use with lion that could help me? I also get an error message sometimes that says (-50).