Thanks loeee,
I already found a nice little freeware icon extractor at
http://www.iconsucker.com. It certainly explains the errors - some of them simply don't have an .ico at index 0 (nothing we can do about 3rd party .dll's) and some have 'icons' which are actually bitmaps (so InstallShield can't find them - you will need something like C++ to see these). Neither fills me with happiness...
I wondered why it would try to to extract these icons when copying the file to the correct location, and having a registry entry to boot would serve the purpose - Yet another case of IS trying to be too clever methinks. Probably to do with the 'Advertising' features that 'might not be installed' - but quite frankly I can't be bothered to investigate this bug-ridden mess any longer!
stillstuckinluton