This is weird. Before sending the copy file to you I opened it , went from the pages tab to the index tab and it crashed immediately. So I sent it off with confidence. Following your reply I tried it again. It will not crash. I went to the original document. It will not crash. I have been working on this document over the last four months but cannot recall when it started crashing. It was doing it regularly however, frequently enough so I never switched from pages to index without saving first. When it crashed I might normally just loaded my saved copy though sometimes I used the system recovery back up. Of course it was retired with the pages tab showing and it always the let me switch to index without crashing that time. I have no document of comparable size, certainly not with an index anything like this one. Unfortunately for your investigation I am at the final proof read stage and so will not be working on this file very much.I have sent the latest crash report via your dropbox. Let me know if you need more - I have lots!