Solution : https://service.sap.com/sap/support/notes/647878 (SAP Service marketplace login required)
Key words : 
spa/gpa crm_url_buffer_off = 'x', attached correction instructions, symptom incorrect buffering, incorrect portal role, terms url generation, url generation, role assignment, deactivated buffering, single roles, object link
Related Notes : 
       
| 1156745 | CRM 4.0 SP Stack 15 (07/2008) Release & Information Note | 
| 897807 | CRM 3.1 SP Stack 12 (12/2005): Release & Inf. Note | 
| 844193 | CRM 4.0 SP Stack 09 (07/2005) Release & Info. Note | 
| 844192 | CRM 3.1 SP Stack 11 (06/2005): Release & Inf. Note | 
| 797957 | CRM 3.1 SP Stack 12/2004 (SAPKU31010): Release & Inf. Note | 
| 797340 | CRM 4.0 SP Stack 1/2005 (SAPKU40008): Release & Info. Note | 
| 761607 | CRM 4.0 SP Stack 9/2004 (SAPKU40007): Release & Info. Note | 
| 755934 | CRM 3.1 SP Stack 07/2004 (SAPKU31009): Release & Info. Note | 
| 754723 | CRM 4.0 SP Stack 9/2004 Support Release 1: Release Note | 
| 743291 | CRM 4.0 SP Stack 6/2004 (SAPKU40006): Release & Info. Note | 
| 711716 | CRM 3.1 SP Stack 03/2004 (SAPKU31008): Release & Info. Note | 
| 709921 | CRM 4.0 SP Stack 4/2004 (SAPKU40005): Release & Info. Note | 
| 696262 | CRM 4.0 SP Stack 1/2004 (SAPKU40004): Release & Info. Note | 
| 683842 | CRM 3.1 SP Stack 12/2003 (SAPKU31007): Release & Info. Note | 
| 677456 | SAPKU40003: Support Package 03 for CRM 4.0 | 
| 663180 | Support Release 01 for CRM 3.1 | 
| 653691 | SAPKU31006: Support Package 06 for CRM 3.1 | 
| 651069 | SAPKU40002: Support Package 02 for CRM 4.0 | 
| 644954 | |
| 633492 |