An error occurred while loading the authentication page when adding Sina Weibo (新浪微博) account

[Sah Lee]

To reproduce:
1. Install account-plugin-sina package.
2. Click "Add account..." in the left panel of "Online Accounts", then choose Sina.
3. Type in username and password in the OAuth page, then click "登录并授权" (Login and Authenticate)
4. Wait a short while and see the message "An error occurred while loading the authentication page."

Below please find the last few lines of the output from signon-ui (with SSOUI_LOGGING_LEVEL set to 2).
browser-request.cpp 117 acceptNavigationRequest QUrl( "http://api.t.sina.com.cn/oauth/authorize" )
browser-request.cpp 324 onLoadFinished Load finished false
request.cpp 128 setWidget Widget already set
browser-request.cpp 305 onUrlChanged Url changed: QUrl( "http://api.t.sina.com.cn/oauth/authorize" )
browser-request.cpp 324 onLoadFinished Load finished true
browser-request.cpp 693 initializeField Couldn't find element: "input[name=userId]"
browser-request.cpp 693 initializeField Couldn't find element: "input[name=passwd]"
cookie-jar-manager.cpp 132 save saving to "/home/sah/.cache/signon-ui/cookies/83.jar"

ProblemType: Bug
DistroRelease: Ubuntu 13.04
Package: account-plugin-sina 0.10bzr13.03.26-0ubuntu1.1
ProcVersionSignature: Ubuntu 3.8.0-29.42-generic 3.8.13.5
Uname: Linux 3.8.0-29-generic x86_64
NonfreeKernelModules: nvidia
ApportVersion: 2.9.2-0ubuntu8.3
Architecture: amd64
Date: Mon Aug 26 12:44:48 2013
InstallationDate: Installed on 2012-08-12 (379 days ago)
InstallationMedia: Ubuntu 12.04 LTS "Precise Pangolin" - Release amd64 (20120425)
MarkForUpload: True
ProcEnviron:
 TERM=screen
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: account-plugins
UpgradeStatus: Upgraded to raring on 2013-04-26 (122 days ago)