Not possible to delete a line in the Material Receipt window, when the receipt line has been created using the dialog Create from using an invoice line.
When deleting the receipt line, the following error is shown:
Record not deleted - dependent record found: ERROR: update or delete on table "m_inoutline" violates foreign key constraint "minoutline_ ...
This is the case when you have created the line by mistake! The workaround is to void the material receipt.