I use the Windows version but I doubt it matters. I use the Quark defaults for color management. You may want to reset them to that for what goes on below. And it may be that you will need to rebuild your preferences.
But first, in Q 2015, you could try rebuilding the document's preview cache. Which is the first thing I would try. Open Q without a document open. Use the File menu, Open selection. Select the document, hold down Opt/Alt (Mac/Windows) and choose to open it. This should rebuild that documents image previews.
Does that work? I'm in between meetings and so will check back later.