Delete file dialog box

I have several sites set up in my Dreamweaver, and on just one of the sites, when I go to delete a file, I don't get the dialog box that pops up and shows me all the pages that reference that file, instead I get just the "Are you sure you want to delete? box like it is an orphan file, though it is not. Does this for any file on the site.

Anyone have any ideas why only one (out of my 20+) sites would not check for reference links before allowing me to delete?

Thanks,

John