Solution : https://service.sap.com/sap/support/notes/632853 (SAP Service marketplace login required)
Key words : 
attached source code corrections, 'sales contracts' application, product selection leads, problem occurs due, upward compatible, crm release 4, support package 02, advance correction, prerequisites, processing
Related Notes : 
       
| 634869 | SAPKU40001: Support Package 01 for CRM 4.0 |