VS2012 - Always open C++ project files for edit when opening solution

[GoogleCodeExporter]

What steps will reproduce the problem?
1. Open a solution file in Visual Studio 2012 RC that contain a mixture of C# 
and C++ projects
2.
3.

What is the expected output? What do you see instead?
I would expect that opening a solution would not need to open project files for 
edit.
In fact all our C++ project files (*.vcxproj and .vcxproj.filters) and the 
solution file (.sln) itself is opened for edit. 
If you diff the files in the p4 client, that have been no modifications.

What version of the product are you using? On what operating system?
I'm using the latest NiftyPerforce source code, on Windows 2008 R2

Please provide any additional information below.
In the output window, you can see that it is trying to add all the project 
files and for most it reports that it cant add an existing file. 

Surely during a solution load, the plugin shouldnt attempt to add new 
files/projects to perforce?

Original issue reported on code.google.com by [email protected] on 14 Aug 2012 at 11:21