[dnanian]

Hi, neuralgia. You're getting a crash and the system is locking up? I really don't think this has anything to do with permissions.

Rather, it sounds to me like your Acomdata drive is locking your FireWire bus. This wouldn't be hugely surprising, since Acomdata is known for using Oxford "compatible" FireWire bridge boards, usually either Initio or Prolific (I believe the latter). These non-Oxford bridges aren't fully compatible and, in some heavy use situations, can cause this exact kind of problem.

Another possibility is that the drive in the case has bad spots, and is causing the bus to lock as the controller retries its write or read.

Finally, it could be another FireWire device (iSight/iPod) causing problems on the bus by drawing too much power or causing voltage fluctuations.

So, the first thing I'd do is simplify FireWire to just this one drive, and then use Disk Utility to erase and ZERO the FireWire drive. This should remap any bad sectors. Make sure to use the "Apple Partition Map" partitioning scheme, should you have a choice.

When that's done, give it another try, and see if it works better.