Indesign CS4 won't retain passwords for placed PDFs

Question

Hi,
I've just upgraded to CS4 from CS2 and I'm having a problem with placed PDF files with password protection.
I wonder if anyone knows why CS4 seems unable to retain passwords for secure PDF files that I have previously placed. Every time I open a document CS4 brings up a 'PDF security password' dialog and I have to enter the password for every placed secure PDF file in the document – no matter how many times I input the passwords and save the document it still happens.
I never encountered this problem in CS2, all I used to do was place a PDF, enter the password for the secure file and then the next time I opened the document with the placed PDFs it would just open without being prompted for the passwords – CS2 just 'remembered' them or something.
There's probably a setting for this somewhere, but I can't seem to find it, so any help with this would be appreciated.
Thank you

Answer 1

Thanks for your replies guys, I think that a little more information about what I'm doing might help you understand my situation.
I am the creator of the PDFs, which are adverts, and these are secured with only one password (for permissions) in my workflow to allow them to be proofed to the client (but to prevent them from being passed on and subsequently altered by third parties.) The adverts are subsequently placed into an InDesign document for a publication which I solely produce.
Previously, when placing these files in InDesign CS2 you only had to enter the permissions password once to place the file and from then on InDesign CS2 did not require the password to be entered again even if you closed the document and re-opened it (unless the artwork had been modified).
I've been using CS2 with this workflow for years and there's never been a problem with my PDFs – not event at the pre-press stage as I generate a high res PDF file for the entire publication and upload this to repro with whom I have a close working relationship and I'm certain that they would have informed me of any problems. Although I think that the final PDF would not be affected by passworded files?
I quite agree, I wouldn't expect someone else to place a file that required a password to do so – but that's not the case here. I'd like to understand why CS4 (and interestingly it seems CS3) doesn't retain the permissions password after it has been entered in the first instance – in the same way that CS2 did. It's inconvenient to have to enter it for each advert in the document every time I re-open it.
Yes, I could remove the security, but for me, that seems to defeat the object of being able to generate just one PDF file in the first place to use in my workflow.