Solution : https://service.sap.com/sap/support/notes/1068662 (SAP Service marketplace login required)
Key words : 
mm - dynamic user settings, personal settings, higher version, transaction me51n, default values, terms esdus, automatic conversion, solution implement, attached program, table esdus
Related Notes : 
       
| 1088904 | Add. info. on upgrading to SAP ECC 6.0 SR3 ABAP | 
| 961410 | Add. info. on upgrading to SAP ECC 6.0 SR2 ABAP | 
| 938706 | ME21N: Default values disappear after upgrade | 
| 913971 | Add. info. on upgrading to SAP ERP Central Component 6.0 SR1 |