Nothing obvious – in my experience laptops often have weaker peripherals than desktops. I would suggest that you (temporarily) try another computer to see if it is the laptop at fault. Also, try different cables.
Note that an unrepeated firewire cable may not be longer than 4.5m (14.8 feet).
You may also want to try the latest beta release, 5.6B2, which has much improved Windows drivers.