same problem here, also with the maxtor one touch storage as firewiredrive. Often the drive disappears after the camcorder (on another firewireport) is switched on or off, apparently it is not safe to turn these firewiredevices on or off with computer running: Usually the external drive recovers after reboot, but I allready had to format the drive once because bootsectors became damaged.
I would also like to know if changing DMA mode helps, and how to do that.