> Er ... sorry that last email should read ".... Phil Wyett's suggestion" in this thread.
Yes, trying Phil's suggestion and will report back once I have had the time to explore it properly (several systems now exhibiting this problem). As a teaser, it seems that even software-properties-gtk creates the trusted.gpg file, but even with that file deleted (as per Phil) and sticking to the terminal and apt-get, I get the same key related errors. In fact if I use software-properties-gtk it seems to jam up on "Refeshing software cache"... has been going on one machine now over 30 minutes.