You could try resetting the InDesign Preferences:
Close InDesign and relaunch it, and IMMEDIATELY hold down Ctrl + Alt +
Shift (Windows) or Cmd + Ctrl + Opt + Shift (Mac), and respond with Yes to the dialog asking if you really want to replace the
If you aren't asked the question, you didn't hold down the keys quickly enough!
Thank you for your suggestion. Unfortunately it didn't work, I got the message saying did I want to delete the InDesign preferences. I confirmed that I did...it continued to load and then I got the same error message again! Any other ideas please?
Have you updated to the latest version of InDesign CC2015.2 ?
It might be worth uninstalling InDesign (from the Creative Cloud App) and reinstalling again.
So sorry for the slow reply. Thank you both for your help - it worked!