Create Patient via FHIR?

Hi,

I've been trying to create a patient using FHIR, but all I seem to get back is:

{"resourceType":"OperationOutcome","issue":[{"severity":"error","code":"invalid","details":{"text":"FHIR create interaction invalid for this end point"},"diagnostics":"FHIR create interaction invalid for this end point"}]}

I've tried a variety of requests and read operations work, but create doesn't seem to. Has anyone run into this? Any ideas? Thanks.