You may find it easier in some cases to use the new [node:13439] instead of OAuth 1.0A.
v1 of the API would often let your calls through in an unauthenticated context if your auth wasn’t quite right – which means that even though you thought it was working it’s possible it wasn’t.
API v1.1 is stricter about auth. I took a very brief look at your code and nothing jumps out at me as being directly wrong, though this is kind of strange – aren’t you setting an Authorization header?
$header = array(buildAuthorizationHeader($oauth), 'Expect:');