This error message occurs randomly after opening up a view:
The cause is unknown at this time.
Solution or Workaround
- Select all themes in the view.
- From the Edit menu, select Copy themes.
- Open a new view.
- From the Edit menu, Select Paste.
- Delete the old view from the project.
- Save the project.
You may want to save the project with a new name to ensure a more stable working environment.