Solution : https://service.sap.com/sap/support/notes/1624441 (SAP Service marketplace login required)
Key words : 
abap runtime error assign_casting_illegal_cast occurs, deleting archived billing documents, function module archive_get_next_record, additional table xyz, archiving object sd_vbrk, data type string, import parameter record_ref, error occurs, exception occurs, report s3vbrkdls
Related Notes : 
       
| 933550 | CPE: Collective Note for ERP 2005 SP05 | 
| 758952 | SD_VBRK: Tables CMFK and CMFP |