FireWire synching is not supported with the new iPod Video, so you won't be able to use the "Griffin firewire to dock cable" to transfer songs (synching your iPod) from a PC or Mac. My wife has a new 30GB iPod Video and we tried to use the Apple FireWire to iPod cable that came with my iPod Mini. Result? Doesn't work. The new iPods just don't have the hardware inside for FireWire, They are USB 2.0 for data/music/video, exclusively.
However, if I use the FireWire to iPod cable with my genuine Apple AC/DC Charger that came with the iPod Mini, charging works fine. You're going to run into problems when you hook up an iPod Video with a FireWire to iPod cable of any description to a computer. But charging an iPod video with the Apple AC/DC charger/FireWire to iPod cable works fine. The Griffin charger sounds similar and should work fine also.
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What's the difference between reality and fiction? Fiction has to make some sense.