Have a look at the Layer to see if it's locked.
Unfortunately, it's not. I wish it was that easy.
Did you click the little down arrow next to the layer name to expand the layer and check the individual objects?
Peter, are you back!
There is also a command under the Object Menu to unlock everything on a the spread, but I would guess you probably don't want to do that for a complex file as it can make selecting more complicated as well as risk having things move accidentally.
@ Derek -- not in a big way. Someone asked me a question, and while I was here I decided to take a look around.
An image could help. But ... (Have to ask about such basics since I don't know your level of experience...)
Are you sure it's not the default black page outline that is always shown (because, yeah, people have asked before how to 'remove' that), and that it is a drawn page item – that is, it does appear when you export the page to a PDF? (Because people have asked about 'removing' guide lines, margins, and "that red line around a page" that indicates bleed & slug.)