Solution : https://service.sap.com/sap/support/notes/540891 (SAP Service marketplace login required)
Key words :
ACCOUNT GROUP of the CONTACT PERSON;KTOKD: STANDARD ADDRESS FIELDSof CONTACT PERSON becomes BLANK.
Related Notes :
| 547705 | SAPKU31001: Support Package 01 for CRM 3.1 |
| 525492 | SAP CRM 3.1: Information on Upgrade |