Some people may be experiencing issues connecting Firewire 400 devices to their new Aluminum iMacs. At least for me, I've been messing around with an iBook G4 and my new 24" iMac, beeing unable to get the iBook connected to the iMac in target mode. After a long lasting call with a very kind person at Apple Support, they contacted some cupertino based third level support guys and came up with a workaround: As they stated, few users are having problems with Firewire 400 devices, even when connecting several Apple computers (depending on model and revision) in target mode to their new Aluminum iMac. As far as I understood, the issue is related to low voltage input (diverging from Firewire specification?!?), meaning, the connected device is not able to deliver enough power through Firewire to work properly. Simply connect the device using a Firewire hub with its own power supply, and things will work fine. At least, they did for me. I hope that helps somebody.