Bom status- Chnage Numbers

Dear Gurus, i have created change number using currect object numbers for for bom and receipe changes. while changing the bom status using c223 tcode, observed that bom status field is inactive. so could not change the bom status to inactive (currently active- greayed out). also checked for some other materials, the status is changable. could not identify the reason why for some materials bom status field is changable and for some it is gradeout. any suggestion?