Why am I receiving resource usage errors like "Failure getting value for disk reads" in splunkd.log?

I keep getting these error messages in splunkd.log: 10-05-2016 15:14:12.491 -0500 WARN IntrospectionGenerator:resource_usage - RU - Failure getting value for disk reads ((D:)), status code is -1073738810 So far I've seen this on full versions on both 6.4.1 and 6.5, so I'm not convinced it's a version-specific error.