For the ASII you just press 999 immediately after restarting the scope
( Look for "Damaged Handbox" in the ASU help file )
This puts it into safeload mode, at which time you can reconnect the ASU updater and do the firmware load. It must be done at 9600 baud so you will have to wait a while
For normal loading of firmware and patches
Starpatch from
http://www.stargps.ca/starpatch.htm
is a much more robust ( and user friendly ) application.
Andrew