recently received this error (below) when submit/ping Yahoo .....
any one face same problem ???
i using this plugin : google xml Sitemaps by Arne Brachhold Errors, Warnings, Notices:

WP_DEBUG was set to false somewhere before. You might not see all debug information until you remove this declaration!
Result (text only):

The following errors were detected: backend fetch error 400 Result (HTML):

<?xml version="1.0" encoding="UTF-8"?> <Error xmlns="urn:yahoo:api"> The following errors were detected: <Message>backend fetch error 400</Message> </Error> <!-- uncompressed Tue Jun 29 15:47:02 PDT 2010 -->