Cannot delete a range name

Workbook contains a number of named ranges where the name is no longer used. I wish to remove the name assigned but not the actual range of referenced cells. When using Name Manager to try and delete the name the Delete button is greyed out and not available. Workbook is being heavily modified from its original form used by another. Is this possibly from a protected area from prior user?
However, I have not had a problem creating new worksheets, cell ranges, etc. Also, even for new ranges I create I am not able to delete the name as the Delete button is greyed. What is going on and how can I delete just the unused range names?
Version is Excel 2010.