ID can't Open PDF files,. only place them, unless you have the PDF2ID plugin.
Is it possible that the .indd file in question isn't really a .indd file at all but something else with file extension changed?
And you need to tell us what version of CS4 and your OS, please.
My Acrobat that is part of CS4 won't open the PDFs created by the CS3 InDesign file. However, I do have the plugin to open PDFs in InDesign and that doesn't work with these files either.
These are files I created so I know that they are InDesign files.
I am running OS 10.6.8 and using CS4.
CS4 6.06 and OS 10.6.8
Can you zip up one each of these files that won't open and post hem someplace?
Either put a link here (which means anyone can download and lok at them), or send the lin to me in a Private Message (click my name to go to my profile).