I opened an existing file (a book with over 200 pages) created in CS4 with CS5.5 to make a few changes. CS5.5 added master page items that had been deleted in CS4, and they were not deletable (even with Command-Shift-Click). Also, CS5.5 crashed as I was trying to delete the items. Fortunately I was able to go back to CS4 and make the changes. I've opened many other CS4 files with CS5.5–any ideas? FYI, it's possible that the CS4 began life as a Quark file many years ago.

Thanks!

A good thought–I didn't know saving as IDML could work both ways (saving back or forward). But it didn't work. I ended up with the same situation–master page items I'd removed in the "good" file that show up in this file and are unselectable. It's also inconsistent. Some pages where I've removed master items look fine; others don't. Very odd.