I have met the same problem, here is the header:
OAuth oauth_nonce=âglxomnct08x0gfialwâ, oauth_callback=âhttp%3A%2F%2Fwww.baidu.comâ, oauth_signature_method=âHMAC-SHA1â, oauth_timestamp=â1373014401â, oauth_consumer_key=â9BFD1XOiVFHrnS7Hw78yAâ, oauth_signature=âQm2WJtOMYAJ8FpOfBAar5THKbdo%3Dâ, oauth_version=â1.0â
nearly the same as the sample in https://dev.twitter.com/docs/api/1/post/oauth/request_token
OAuth oauth_nonce=âK7ny27JTpKVsTgdyLdDfmQQWVLERj2zAK5BslRsqywâ, oauth_callback=âhttp%3A%2F%2Fmyapp.com%3A3005%2Ftwitter%2Fprocess_callbackâ, oauth_signature_method=âHMAC-SHA1â, oauth_timestamp=â1300228849â, oauth_consumer_key=âOqEqJeafRSF11jBMStrZzâ, oauth_signature=âPc%2BMLdv028fxCErFyi8KXFM%2BddU%3Dâ, oauth_version=â1.0â
Do you have any idea of it? BTW, how to post a new topic on Discussions?