DTE.Debugger.Go(False) fails after building externally in a Visual Studio 2008 macro

I am writing a macro to save all open documents, launch MSBuild to build C# projects in parallel, and then run the solution using the debugger. Automating these steps in a reliable way will save my team a lot of time.

My problem is I can't get DTE.Debugger.Go(False) to work when the external build changes the output files.

Error

Unable to cast COM object of type 'System.__ComObject' to interface type 'EnvDTE80.DTE2'. This operation failed because the QueryInterface call on the COM component for the interface with IID '{2EE1E9FA-0AFE-4348-A89F-ED9CB45C99CF}' failed due to the following error: System call failed. (Exception from HRESULT: 0x80010100 (RPC_E_SYS_CALL_FAILED)).

OK

Here is the macro definition I have:

Private Function SaveAllDocuments() As Boolean
    Dim doc As Document
    For Each doc In DTE.Documents
        If Not doc.Saved Then
            If (doc.Save(doc.FullName) <> vsSaveStatus.vsSaveSucceeded) Then
                Return False
            End If
        End If
    Next
    Return True
End Function

Sub ParallelBuildAndRun()
    If (SaveAllDocuments() = True) Then
        Dim p As System.Diagnostics.Process
        Dim fileName As String
        Dim args As String

        fileName = "C:\Windows\Microsoft.NET\Framework\v3.5\MSBuild.exe"
        args = "/p:Configuration=""" _
            + DTE.Solution.SolutionBuild.ActiveConfiguration.Name _
            + """ /m """ + DTE.Solution.FullName + """"
        p = System.Diagnostics.Process.Start(fileName, args)
        p.WaitForExit()
        If (p.ExitCode = 0) Then
            ' Not even the evil DoEvents helps here.
            'Application.DoEvents()

            ' This line will crash if the output files that are 
            ' going to be debugged changed while in this macro
            DTE.Debugger.Go(False)
        End If
    End If
End Sub