I am trying to import some information into items -- when i attempt to import the information on an inventory item, it works fine -- but when i do the same thing for assembly items, it fails.  Basically i have some custom fields that source from items.  I use the items internal id to update the custom field -- it works fine on inventory items but doesn't on assembly items -- any thoughts on the problem or a work around?

I do have two different imports set up -- one for inventory items and one for assemblies but it fails on the custom item on the assembly items stating "invalid custitem_field reference key.  Even though the value is a valid internal id.