Visual Studio 2008 Debugger incorrectly shows C++ as the language when in C# solution

I've had this issue for some time, but it is blocking me now.

An开发者_运维知识库y solution I edit or create is stuck in C++ mode. The Stack Trace shows "Language" as C++ and the watch behaves differently--shows memory addresses, etc.

ASP.NET debugging is also effected in that it doesn't work at all. However, this may be unrelated.

I've reset my settings to default and perused every option in the Tools > Options dialog. I'm running out of ideas.

Any clues?

UPDATE: I've completely uninstalled VS 2008, and then re-installed and applied SP1. Same issue occurs.

I then removed the following directories: C:\Users[username]\Documents\Visual Studio 2008 C:\Users[username]\AppData\Local\Microsoft\VisualStudio C:\Users[username]\AppData\Roaming\Microsoft\VisualStudio

No change. Issue still occurs.

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We can verify the solution and project types. Open the .sln file in a text editor. Look for Project tags like this:

Project("{8BC9CEB8-8B4A-11D0-8D11-00A0C91BC942}") -- indicates a C++ project
Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") -- indicates a C# project

These projects are listed in the registry at HKLM\SOFTWARE\Microsoft\VisualStudio\9.0\Projects. If you open this key, you should see these and many other project types listed:

{66A26720-8FB5-11D2-AA7E-00C04F688DDE} Solution
{F184B08F-C81C-45F6-A57F-5ABD9991F28F} VB
{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC} C#
{8BC9CEB8-8B4A-11D0-8D11-00A0C91BC942} C++
{E6FDF86B-F3D1-11D4-8576-0002A516ECE8} J#
{E24C65DC-7377-472b-9ABA-BC803B73C61A} Web

I'd verify the C# GUID is there, and that its values map to things that look like C#.