When importing to a version 4 module with Visual Integrator you may receive an error message "Invalid Field ____ [field name] is read only"
Solution:
Remove the Line key fields from the import job.
Scan the VI job import lines and look at those starting with L
If the line is a key field which also appears in the Header, then you can try removing the duplicate line from import
Note: This may be an issue that appears after upgrading from 4.05. We have noticed this issue with clients upgrading from 4.05 to 4.30.