Thanks all of you for your comments. I'll address each relevant point below:
artie505: that .pref file is present on my regular startup drive too, but not on the eDrive.
Jchuzi: I'm aware of the two different files and their locations, but neither one is present on the eDrive, where after all DiskWarrior never even ran beyond throwing that error message and quitting when the error was dismissed.
DKMarsh: yes, I'm booting from the eDrive and looking in /Library/Preferences on that same eDrive (as well as everywhere else, for that matter: no joy).
Virtual1: I was wondering about write privileges myself; only the system is listed as having write privileges for the eDrive and /Library/Preferences. Obviously, I wouldn't ask Micromat to help me with something they specifically recommend not to do. And yes, despite the wording of the error message, there may be critical System components missing to allow DW to run. But wouldn't this apply to anyone trying to do this? Hence my original question: did anyone manage to run DW from the eDrive? While I'm entertaining any and all comments, ideally I'd like to hear from one of those successful users 'of no small number'...
Btw, this scenario plays out identically on an iMac G5 iSight running Mac OS X 10.4.11, and on a 15" early 2008 MBP running 10.5.8, both (including their eDrives) with the latest OS and TTP updates applied.
