I guess this one sorta stumped you guys a bit or you just don't care, but you seem like nice people so I'll assume the first.
I started thinking the other day whether or not having other things plugged into the firewire ports could cause problems. I usually have either my iPod or iSight plugged in. I remember hearing or reading something a while back that said not to have anything else plugged in while using an external hard drive. Not sure though. Worth a shot if no one else has any ideas. Any thoughts would still be appreciated though.