Self reference doesn't match document location
rel="self", the href attribute is expected to identify
a resource equivalent to the containing element.
Check the document referenced by the href attribute. If it is not the intended feed, correct it.
This may not be a problem. At the current time, the feedvalidator does not probe to assess equivalence of documents.
Not clear? Disagree?
You might be able to find help in one of these fine resources.