Why doesn't standard cost update to the latest price entered in Item Maintenance?

I am wondering why the Standard Cost does not update in the Item Maintenance window.  The item is set to Standard Cost in the Valuation slot, but when we enter a new updated cost in the "Last Costs" category, the "Standard Cost" space, in the Purchases category does not update to the current cost.

Would someone be able to tell me if they have run into this in the past and how it was resolved.

Thanks,

Martin