Just wondering is the file your trying to open created originally on the mac or on the PC and secondly is the file on a network drive with only read only access.
Thank you mckayk...
Document is originally created on Mac and accessing it from my desktop.
I am using
MAC OS X on Intel Core i7
and document is created in InDesign 5.
Problem due to version change....???
Files of older versions always open "as copy" -- if you look in the window title, it will say "Yourfilename.indd -- [Converted]".
If you open this file and then save it back under your current version, it will behave as expected.
Thank you Jongware...!