This occurred due to manual changes/updates to the tables, but may be worthy of consideration.
If the ToolbarView is set to true and no View exists (note, we didn't find where the toolbar view is actually stored), an error occurs indicating that the toolbar can't be found. The OnValidate event on the page should be sure to set ToolBarView flag properly.
The message cannot find toolbar should be enhance to include the name of the toolbar which cannot be found. If the field is empty, <Empty> or some such should be displayed.
This was found in ISA 6.1