Hi Mike & Doug:
I think I see why you have different experiences.

Mike, I believe, is accessing the Reorder information by selecting an Item in Item Maintenance, editing it and selecting the "Reorder" tab. Like Mike, I cannot delete those dates. But I found that if I access the Edit | Item Maintenance | Edit Reorder Data menu option, dates can be deleted. I think that is what Doug is describing. I don't know why there is a difference in behaviour.