Solution : https://service.sap.com/sap/support/notes/215074 (SAP Service marketplace login required)
Key words : 
affects cross-client tables, cross-client tables, data inconsistencies result, arising inconsistencies subsequently, additional key words, currency key, local currency, productive clients, question arises, system lock
Related Notes : 
       
| 183158 | LC changeover to euro: Cluster functions | 
| 169094 | Clust:Program terminat.w/'Import of Cluster No. XXXX failed' | 
| 121626 | Euro LC changeover:important Support Packages info. |