I uninstalled Battle Net. Then ran Overwatch which triggered a reinstall. This completed okay and then it ran. I was able to run Overwatch, but did see more of the same No Disk -> “Exception Processing Message” errors. I quit Overwatch and Battle Net. On launching Overwatch again (which triggers Battle Net start) I am back to square one with the errors. I can see the Battle Net login after a dozen or so errors, and after logging in, the application never starts - it is an endless loop of these No Disk errors.