Very strange error when trying to build VC7 project

[MHolmes]

I am trying to build a VC7 project here on my build box via VisualBuild. Any time I attempt to build a VC7 or VCs7 project, I get the following error:

Building...
Command: "C:\Program Files\Microsoft Visual Studio .NET 2003\Common7\IDE\devenv.com" 
"c:\source.vs2003\build.source.xipay\\Tools\XiSQLBot\XiSQLBot.vcproj" /rebuild "Release" /project 
"c:\source.vs2003\build.source.xipay\\Tools\XiSQLBot\XiSQLBot.vcproj"

Microsoft (R) Development Environment  Version 7.10.3077.
Copyright (C) Microsoft Corp 1984-2001. All rights reserved.

Invalid project

Usage:
devenv  [solutionfile | projectfile | anyfile.ext]  [switches]

There is quite a bit more text that follows, but it seems to all be usage information. Please note, these projects work just fine on our build box using VisualBuild and when opening them in VC7 by hand and compiling them. There is nothing wrong with the project files!

Any ideas what would cause this?