How to delete an inventory item from maintenance BOM

Hi,

We disabled an item in inventory module (which was appearing in an activity), now if we are generating PM against this activity we are getting error message. We tried to disable this item in maintenance bom by using effective date from/to option but this is not serving the purpose.  

The other option was to delete the item from maintenance bom, we tried to delete (Enterprise Asset Management -> Activities -> Maintenance BOM) but item still appearing in maintenancce BOM.

Note: delete button is available, on pressing delete button i am getting message to select delete group (which i am slecting - just created from same window) on save i am getting message of transaction completed but still item is appearing in maintenance bom.