I do not really know how to deal with the error message. I would start from the 
very basics:

  - Stop the NW services
  - Copy the nsr path to a safe location
  - Delete the directories
       /nsr/index
       /nsr/logs
       /nsr/mm
       /nsr/res
       /nsr/tmp
  - Start the NW services (this will result in a fresh installation)
       - If NW works now, the program files are fine and the trouble is most 
likely with the media index
            In this case you must recover the last known good bootstrap saveset
       - IF NW does not work, reinstall it 
            Then reactivate the saved databases (forget /nsr/logs & nsr/tmp)

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