Loading Error in VSU WPF Designer

I'm using Visual Studio Ultimate 2010 (32-bit). I am building a project in Visual Basic 2010 and WPF 4.

I had the WPF designer working just fine until yesterday, when I tried installing the Silverlight 4 Tools for Visual Studio 2010 from Microsoft. However, as soon as I installed it, I started getting the following error in the designer every time I tried loading any WPF window. I unin开发者_运维知识库stalled the tools and reinstalled Visual Studio Ultimate, to no avail.

Problem Loading The document contains errors that must be fixed before the designer can be loaded. Reload the designer after you have fixed the errors.

However, the project compiles and runs without incident, and there are no errors being shown in the XAML text. Here is the first part of the XAML for each window, in case this helps.

<Window x:Class="FRM_TEACHER"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="FRM_TEACHER" Height="Auto" Width="Auto" WindowStyle="None" WindowState="Maximized" WindowStartupLocation="CenterScreen" Background="Black">
<Grid Width="640" Height="480">

Help?

After uninstalling and reinstalling the Silverlight 4 tools, it worked.