InDesign file that refuses to open in usable form

I am doing a Lynda.com course Learning InCopy. All was going well until lesson 2, when I had to open one of the exercise files ''story.indd' and found that although it opens all the text is greyed and a little window informed me "because this document contains no InCopy stories, galley view and story view are not available'.  I can select the various 'stories' on the spreads shown but cannot edit them. I have contacted Lynda.com but they say they have tested the exercise and it works fine for them. They advised me to download the latest version of InCopy, but I have that so that can't be the source of the problem. Any ideas? If I am having this problem with a 'test' file I fear I may have it with real jobs (I am a freelance editor)/