This is coming from a script. Chances are that if you open File Options from the file menu, you'll find there's a script specified to run each time the file is opened.
Inside this script is a step that is trying to modify a field, probably a set field step, and the field is from a table (table occurrence actually) that is not the specified table for the layout that is current at the time the script is performed nor from a table occurrence that is related to the layout's table occurrence.
Figure out which layout was current when the script was performed and use the name selected in layout setup | Show records from to find the box (the table occurrence) of exactly the same name found in Manage Relationships. Note what occurrences are linked to it. Then compare this to the steps in your scripts looking for a set field step where the table occurrence name from the target field is not this same name and not one of the occurrence names linked to it in a relationship. The most likely fix for your script is to put a go to layout step at the beginning to make sure your script is performed from the correct layout every time.
The target field in a Set field step is shown in fold face on the next line:
Set Field [TableOccurrenceName::FieldName ; //some expression goes here ]
You need to check the text to the left of :: to see why you are getting this error.