I have used this program since ID 1.0 and have never encountered this until recently. I am using CS5, created the document in CS5, have opened it and edited in many times. It is a 253-page book and I am at wit's end. Please help! Adobe, what the hell? I have Mac OS10.8.3. Don't make me go back to Quark!
I just fixed it myself, by reading the forum posts before mine, and used the dialog box, selected the "open as copy" radio button, and it appears to be the solution. Thank you Adobe Community for enabling me to look within (the forum posts).