This issue occurs if you have any files open in InDesign from network server and network connection is lost. To resolve this, either you need to copy document locally and open it from there or make sure network connection to the server is maintained while document is open.
What OS do you have?
What InDesign version do you use?
I work normally with El Capitan and CC2015.x. But when I work with CS6 I get often this message if I have not saved the file for a longer time or when the Mac awakes from sleeping.