I found the following some time ago now on a PCAdvisor magazine forum which worked for me when I had the same problem.
Also worth a try is simply to 'click the 'back' box in the wizard and it runs again.
"To Downgrade SpeedTouch 585 v.6 Firmware
Connect the unit to the computer via ‘Ethernet port 1’ ** MUST be port 1
Have the ‘SpeedTouch Upgrade Wizard’ interface open; either from SpeedTouch CD or file.
Begin with the unit powered ‘Off’ via switch at the back
Using pin/pencil push the ‘Reset’ button and hold it in
Keeping the ‘Reset’ button pushed in, power ‘On’ the unit.
Do Not Release the ‘Reset’ button for 15 seconds.
The ‘Power’ light initially goes ‘amber’ and then both ‘Power’ and ‘Ethernet’ lights should flash between ‘red’ and ‘green’
Run the ‘SpeedTouch Upgrade Wizard’.
You only have around a minute to start the wizard before the SpeedTouch reverts to the ‘normal’ bootup and the downgrade will fail if this happens."
Hope this helps.
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