service.getAccessToken() is throwing Exception

Question

I am using scribe 1.3.3 Oauth library for uploading Image to twitter.

I can able to get RequestToken and verifier, but still

 Token accesstoken=oAuth.getAccessToken(requestToken, verifier); is throwing exception

EXCEPTION:

org.scribe.exceptions.OAuthException: Response body is incorrect. Can't extract token and secret from this: '<?xml version="1.0" encoding="UTF-8"?>
03-05 15:52:24.810: E/AndroidRuntime(28777): <hash>
03-05 15:52:24.810: E/AndroidRuntime(28777):   <request>/oauth/access_token</request>
03-05 15:52:24.810: E/AndroidRuntime(28777):   <error>Invalid / expired Token</error>
03-05 15:52:24.810: E/AndroidRuntime(28777): </hash>

I cant able to understand what this exception is and why it is occuring.

please suggest me in solving this issue.

Thanks in advance