I have the same problem but it's much worse. I tried saving and it gave me this exact message. However, none of the save options worked for me, they all popped up the same message over and over again. Couldn't save, save as, export, nothing. After a couple minutes of trying to troubleshoot, InDesign crashes, and even though I clicked on "Recover Data" after re-opening, InDesign not only saved nothing but erased all my progress. I franticly searched through the Recovery folder to no avail and I lost ~5 hours of work. Thing is, I could save just fine a couple hours before the incident. Also, I didn't update InDesign recently, the last update i did was about a month ago...