It's under Edit->Color Settings
What are your settings in Bridge?
I tried to replicate this making a new image in Photoshop filled with 100% K. I saved it as a Photoshop PDF. Then made a new document in Indesign and made the entire background 100% K. Then I placed the Photoshop PDF in the middle of that page. I see no difference between the two.
Still think it might be a color management issue.