I should clarify that I am working with Id CC (Creative Cloud).
One respondent in the mammoth, multi-page forum I am working my through, describes CC as the “Windows Vista of the Adobe world”. Another likens it to “someone running around with flame thrower”. (https://forums.adobe.com/thread/1241139?start=160&tstart=0 accessed on 4 Dec 15)
And still no one at Adobe can solve the problem. However, with the many commentators there seems to be a consensus that it is legacy files that are the problem.
This is particularly germane for college students as they have a previous version on SDC computers and many may have the newer version on their own machine.
The advice appears to be to save the legacy files as .Idml before input into CC.
Another view, however, is this is conflict with Fonts
“We have had this problem (inDesign not able to save or undo) when using InDesign along with Extensis Universal Type Server (or Suitcase) – Basically the root of the problem is with Microsoft Fonts in the Library (the ones installed automatically when you install MS Office).
The solution we found was to remove these fonts from the local drive and create a font set on the Universal Type Server to manage the MS fonts.
1. Go to: Macintosh HD/Library/Fonts/Microsoft
2. copy the entire folder to: Macintosh HD/Library/Fonts Disabled (just in case you need them later)
3. also copy the entire folder to wherever you keep your managed fonts (i.e. not system or local fonts) – we use a network location, but you may have a local folder if you’re not running a network type server (i.e. suitcase).
4. Then delete the original “Microsoft” folder from: Macintosh HD/Library/Fonts
You’ll need your admin password to authenticate this. Don’t worry, you have a backup in Fonts Disabled!
5. Create a new set in Extensis UTC/Suitcase and drag the Microsoft Fonts in from your font library (Not the Fonts Disabled folder – i mean wherever you keep your managed fonts)
6. Permanently Enable all fonts within the set.
7. Restart your machine.
This instantly fixed the issue for us!”
This appears to be the most likely solution but does not come from Adobe.