Many thanks to the various prompt responses to my query.
Mark Secker pointed me to the cause by noting that the bridge is powered from the FW cable. I had assumed that light on meant power on. In fact the power plug, in amongst a mass of plugs and cables behind my workstation had been knocked by my dear wife with the vacuum cleaner, a job which of course I should do myself in this area!! It was just this one that had been merely nudged, all the myriad other units were operational!
A relief, though everything is backed up.    Thanks, Mark and others!
Severin Crisp
________________________________________________________

                    Assoc Professor R Severin Crisp, FIP, CPhys, FAIP
       15 Thomas St, Mount Clarence, Albany, 6330, Western Australia.
                      Phone  (08) 9842 1950   (Int'l +61 8 9842 1950)
                             email  mailto:[EMAIL PROTECTED]
                            Web pages http://www.JennyCrisp.com.au
                               &  http://members.westnet.com.au/Crisp
________________________________________________________