Have the exact same issue in Snow Leopard (10.6.8). Tried many different cables and configurations (daisy-chain/direct/different cables/lengths/colors, Disk Util format/Lacie drive app format, running with/without Lacie desktop manager – just what I want…another app running all-the-time!, etc, etc.) I have other fire-wire drives on the same Mac (i.e. daisy-chain) working flawlessly. I contacted Lacie and after suggesting most of the things I had already tried, they wanted to set-up a return/replacement. The drive seems to work fine as long as it’s turned-off during boot and I have neither the time nor desire to play “mail-tag” with Lacie for a month. I just won’t buy another one. It’s a shame, I thought they had a good reputation, and maybe they do? I’ve had many fire-wire drives on many Macs over the past decade and none have needed babysitting like this one. (…SCSI: ON before boot, Lacie: OFF before boot…got it! I think.)