The transparency problem seems to be initiated by an interaction with other pages in the document. If I delete a range of pages, or move the troublesome page earlier in the document, I am able to create new transparent content that will display when PDF'ed, but the existing transparent content still exhibits the same problem.

Somehow specific content on the page is retaining the characteristics from this interaction with the other pages. Content has been moved to another layer without success, and prior to the page move new content was created on another layer without success.

I have uploaded samples including the original 52 page InDesign document with all confidential content removed except for some transparent objects on page 52. In this current state the existing objects and and new transparent objects will not display in the PDF.

http://www.sendspace.com/file/rrfgwi

The remove clip is an excellent fix suggestion and I hope to use it versus the recreate from blank document method. This will help me resolve the issue when it is brought to my attention, but I still hope to gain some understanding of the root cause.

Yes, I have tried removing all objects and creating new ones without success. I also tried the IDML or exchange file types and it did not work. I have posted a (zip) link to the InDesign files and PDF, and my more recent post explains the progress of my testing. Thank you again for your input.

I appreciate someone with an advanced knowlege taking a look at these files. Due to our workflow we need to maintain transparency downstream. We do our best to retain live transparency until the file hits the RIP, so dropping our compatability level is unfortunately not an option. Since the problem is idiopathic and fairly uncommon (I hope I didn't just jinx myself), I will need to deal with the work around until we can find the direct cause of the problem.

Thank you again for looking deeper into the files. I will update if I discover anything new about them as well.