All the sudden I cannot edit a document that I have been working on for weeks. I can't Save As and I can't Save any edits. What gives?
When I tried to export this as an IDML I discovered that my target disk had somehow become locked/inaccessible. When I just saved the file to another disk, it seemed to save just fine. I suppose this was the problem all along. I'll have to investigate that further. Thanks for the prompt!