'Unknown error' with saving file after upgrading to CC 2017
I just upgraded to Illustrator CC 2017.
Now my files will not save, I get the notification: 'An unknown error has occured'.
- I tried saving with a different name. No success
- I tried saving with deselecting the 'Create PDF Compatible File' option. No success
- I tried removing the Adobe Illustrator 21 settings folder in Preferences, but keep having the problem.
I am running 
Does someone know a solution?
Please without outline stuff, as this is a work file.
Thank you.