Does Make VS 2005 action support x64?

[kinook]

Yes, it sounds like an issue with Visual Studio (msbuild and/or devenv) when building from the command line, which isn't always identical to building in the IDE (another possibility is some sort of problem with the project file if you manually edited it). You can verify that it's not a VBP issue by checking the 'Display command-line...' checkbox on the Options tab of the Make VS.NET action, rebuilding the step, then copying and pasting the msbuild/devenv command-line from the build output to a batch file like this:

<msbuild/devenv command here>
echo exit code = %ERRORLEVEL%

and then running the batch file from a Command Prompt. If the problem (errors/warnings or non-zero exit code) occurs outside of VBP, you'll need to open a support incident with MS to investigate the problem.