This is a new feature in InDesign CC. It could be a bug. Does this happen in just one file, or in other files? What operating system?
Most of us haven't had a chance to use this feature yet.
I saved an additional copy of the file and was getting the same result - but don't have any additonal files to work with at the moment. I'm running Mac 10.8.4
OK I managed to solve this. I was working with text from an InCopy document - which wasn't checked out. Makes sense that InDesign couldn't do the job - but may be an error or warning would be better than straight to crash!