Unable to get access token from Facebook. Got an OAuthException says "Error validating verification code"

I am using java and the purpose of my demo application is simple: Update user status. I followed the Server-side Flow on page http://developers.facebook.com/docs/authentication. I got the auth dialog, facebook lead to the callback url and I got the code in my callback page. Then I failed when I try to generate an access token.

In the guide page, it says the following url could be used to generated an access token:

https://graph.facebook.com/oauth/access_token?
     client_id=YOUR_APP_ID&redirect_uri=YOUR_URL&
     client_secret=YOUR_APP_SECRET&code=THE_CODE_FROM_ABOVE

But what happens in my environment is I got the following error message:

{
   "error": {
      "type": "OAuthException",
      "message": "Error validating verification code."
   }
}

I am quite sure every parameter is correct because if I change the client_id value or client_secret parameter, I will got a different error message. The code parameter is what I got from facebook callback. So this should be correct, right? Really can't figure out what is the problem....

Any idea about this? I get stuck here...