Check to make sure that you are looking at the proper page in the book
file, i.e. physical page count, not FM page number. Distiller reports
the page count.
Does that help?
You should be able to tie down the invalid file access to a particular condition in a particular file, then start checking all the conditions and where they're applied.
Good luck
Ian
I've not seen it mentioned that you have all the files open before beginning the operation (Shift+File > Open All FIles in Book), and all files saved, no messages in the console window (missing fonts, can't find reference, etc.). If other applications are using some referenced files, perhaps a graphic application has a graphic file open, or a periodic backup operation is reading the file, the conversion operation might fail with this message.
Try turning off all applications you don't need, and use the Task Manager to shut down any unneeded processes or background operations. Be careful not to shut down required processes.
If you can consistently convert the book in such a minimal state, then you've isolated the problem enough to look for the one or several culprits.
Regards,
Peter Gold
KnowHow ProServices