Hi again,
According to SAP documentation, clearly the TAL returnable packaging item should not being invoiced, as it is invoiced later with the Returnable Packaging Issue if the customer does not return the packaging item.
http://help.sap.com/saphelp_erp60_sp/helpdata/en/dd/560051545a11d1a7020000e829fd11/content.htm
You seem to have the right customizing so maybe it is a mistake in standard SAP, because the system should not even try to invoice this item as it is not relevant for invoicing.
In a first step, I would go into copy control configuration between delivery and invoice and mark the item category TAL as "don't copy". This way it will not get copied into the invoice.
In a second step I would invoice the rest of the delivery and afterwards check that the delivery document is "closed" from a document flow point of view (check the SD document flow). If it is the case, then I would close the problem.
Best Regards,
Franck