Visual Studio 2012 The project file "" has been renamed or is no longer in the solution

I had the same problem, and solved it by making sure that every project referenced by other projects were included in the solution.

Right-click on the first project, choose References... and make sure every project listed under References are included. Go to the next and do the same.

That solved my problem with "The Project file '' has been renamed or is no longer in the solution". Not sure about the problem with "A build is already in progress".

I can confirm the_mantrill's scenario. (Posting as an answer, because this wouldn't fit in a comment.)

In my solution, Project A references Project B. For some reason, Project B's Project GUID changed. (I know this can happen, I didn't investigate what caused it in our case.) The solution file had the correct new GUID for Project B, but in Project A's project file, the reference to Project B still had the old GUID.

By unloading and reloading projects in the Solution Explorer, I found that Project A caused "The project file '' has been renamed or is no longer in the solution." Once found, manually updating the Project B's GUID in Project A's project file fixed the problem.

Details:

ProjectB.vcxproj

<PropertyGroup Label="Globals">
    <Keyword>Win32Proj</Keyword>
    <ProjectGuid>{9CF2493A-0C79-88E7-12ED-7DFAEBA8535B}</ProjectGuid>
</PropertyGroup>

At some point in the past, ProjectB's ProjectGuid used to be {d6f1934a-905f-77ca-49c0-164b2171a0f6}. It's now {9CF2493A-0C79-88E7-12ED-7DFAEBA8535B}.

ProjectA.vcxproj – before, causes "The project file '' has been renamed or is no longer in the solution."

<ItemGroup>
    <ProjectReference Include="..\ProjectB\ProjectB.vcxproj">
        <Project>{d6f1934a-905f-77ca-49c0-164b2171a0f6}</Project>
    </ProjectReference>
    :
</ItemGroup>

ProjectA.vcxproj – after manual editing, now works:

<ItemGroup>
    <ProjectReference Include="..\ProjectB\ProjectB.vcxproj">
        <Project>{9CF2493A-0C79-88E7-12ED-7DFAEBA8535B}</Project>
    </ProjectReference>
    :
</ItemGroup>

The problem seemed to occur for me when I had two solution files for different products, but which had several projects in common. These were VS2010 projects that I was opening for the first time in VS2012. When opening the first one all the projects were converted. The problem then arose when loading the second one as some of the projects had already been converted. It seemed to be the project references had been updated in the first solution, but then for the second solution it had to deal with updating some projects but using the already-updated versions of the common projects.

In the end, to solve it I had to remove and then re-add a couple of projects (and the project references) and that seemed to sort it out. It's also worth removing the build folders and the other temporary files (such as .suo) as the state of some of those files affected the project references problem (which I really didn't expect).

delete the .suo and reload worked for me after moving from VSO to onsite TFS had some issues

The project file has been moved renamed or not on your computer