opmnctl start fails when ORA_NLS10 parameter is set

I got into this issue , where in while starting Grid Control components, opmnctl command failed with following errors

./opmnctl start
globalInitNLS: NLS boot file not found or invalid
 -- default linked-in boot block used
XML parser init: error 201.
globalInitNLS: NLS boot file not found or invalid
 -- default linked-in boot block used
XML parser init: error 201.
globalInitNLS: NLS boot file not found or invalid
 -- default linked-in boot block used
XML parser init: error 201.
opmnctl: opmn start failed

On checking environment variables, I found ORA_NLS10 env variable was set. Unsetting it resolved the issue.