@rundenk – what do you see in the preferences, if you restart InDesign with no documents open?
All settings set to millimeters?
If not, adjust them as you wish and quit InDesign. That should reset the preference file of InDesign.
The next time when you add a new document, the settings should be as you want them.
What can go wrong?
InDesign is alerting you that it unexpectedly quit after you quit the app. That would possibly mean InDesign cannot overwrite the old preference settings…
The preference settings are "corrupt". And you have to remove the settings in your file system.
Read/Write permission problems for your preference settings file in the file system.
… ?? Maybe other problems with the new synching feature n case you are using InDesign CC-2014 ?
I thought I had done that but obviously not.
I cant say i fully understand the syncing features either but no doubt that's for another thread.
i did as you inferred.
Reopened indesign and check the settings. They were set at MM and CM. Obviously everytime i had tried to change the settings I had a document open