Solution : https://service.sap.com/sap/support/notes/509044 (SAP Service marketplace login required)
Key words : 
system displays dialog box 'bill, view 'work scheduling', convert planned orders, dialog box, dialog query, planned orders, planned order, transaction co41, material bom, material master
Related Notes : 
       
| 511140 | CO41:Incorr. numbers entered in status line after conversion | 
| 453755 | No status check when converting plnd order to productn order |