Check you have the latest software or firmware drivers from their website at Focusrite.com
Check that the FireWire cable is connected properly.
Try using the supplied power cable.
Try using the other FireWire port found on the back of your Saffire product, and also try different ports (if you have more than one) on your computer.
If you have any other FireWire devices connected, try disconnecting them, as they may be restricting the FireWire bandwidth too much if connectedon the same bus.NB:
You may have more than one FireWire port on your computer. Note that they may be connected to the same bus, even though they appear to be physically seperate. This will be the case if you have a FireWire card with multiple FireWire ports on (all ports on the card will be on the same bus), and is also often the case if you have multiple ports inbuilt on you system.
Increase the FireWire buffer size on your FireWire card, found at C:/Program Files/Focusrite [Saffire product]/Driver/ASIOControlPanel.exe (where [Saffire product] is the name of your Saffire product). Its default setting is 2ms, but you may find that increasing it helps connectivity and will improve audio performance, at the cost of increasing latency.