What have you changed recently? Any new fonts?
OS? Version of InDesign?
Hi again. I have recently downloaded some fonts from Toolkit.
OS X Yosemite. v 10.10.2
Do you mean Toolkit or TypeKit, which is part of CC? See Remove minor corruption by exporting. If that doesn't work, try exporting the text to ID Tagged Text and place in a new file, and if that also fails, try removing the fonts.