从Visual Studio Team System 2008 Development Edition升级到Visual Studio Team System 2008 Team Suite打开WPF Application会发现XAML Design无法加载, XAML文件被视为Text Document打开. 如图:

解决方法:
1. 关闭已经打开的Visual Studio 2008.
2. Micorosft Visual Studio 2008 -> Visual Studio Tools -> Visual Studio 2008 Command Prompt输入:devenv /resetskippkgs
3. Visual Studio Restart.
重新打开WPF Application发现XAML Design加载成功.
resetskippkgs(reset skip packages)的作用是告诉Visual Studio清除所有加载失败的VSPackage，重新加载所有VSPackage启动 Visual Studio.

在Visual Stdiuo产品的Feedback里有好为数不少的人提到(有人提到先repair Visual Stduio 2008 -> VS2008PatchRemovalTool -> reinstall Visual Studio 2008 SP1 -> devenv /resetskippkgs, 个人建议还是先尝试devenv /resetskippkgs不要急于先去repair Visual Studio 2008大费周折):

http://connect.microsoft.com/VisualStudio/feedback/ViewFeedback.aspx?FeedbackID=370988
http://connect.microsoft.com/VisualStudio/feedback/ViewFeedback.aspx?FeedbackID=426806