This has been discussed in many details on forum if you search for it.  Removing and adding client won't fix it.  You either delete the entry from local host resource or you disable nsrauth for good on server (and storage nodes).

Johans,

Please review the following EMC Knowledgebase article for details on resolving this issue:

nsrexecd: SYSTEM error: There is already a machine using the name: "(hostname)"

Article number esg73971

Let me know if this does not resolve your issue.

Mark