Solution : https://service.sap.com/sap/support/notes/747036 (SAP Service marketplace login required)
Key words : 
correct login language     - login language = data language       -, interfaceduring data communication language-based filters ensure, rfc login language field empty, landscape comprising unicode-based systems, mysap erp 2004 environment solution background, unicode         login  language passed, iso latin-1- iso latin-1 characters, multi display multi processing, components     - interface unicode --> mdmp       - user, data transfer       - rfc connnection
Related Notes : 
       
| 1319517 | Unicode Collection Note | 
| 938738 | Syslog CP6: still using ambiguous blended code page | 
| 938737 | Syslog CP6: still using blended code page | 
| 896144 | SAP ERP 6.0 Upgrade for R/3 or ERP MDMP Customers | 
| 745030 | MDMP - Unicode Interfaces: Solution Overview | 
| 548016 | Conversion to Unicode | 
| 79991 | Multi-Language and Unicode support of SAP applications | 
| 73606 | Supported Languages and Code Pages |