The build behaves as if the Visual Studio Add-in is not installed. Builds are not broken up.
The issue is that Service Pack 1 for Visual Studio 2005 breaks the command-line add-in invocation so the command-line add-in is not invoked. See the links below for the Microsoft hotfixes for this issue.
933054 (for Windows XP)
934517 (for Windows 2003, Windows 2008, Windows Vista, and Windows 7)
Note that the various Microsoft support and hotfix download sites can be very confusing regarding this issue. Either hotfix has been shown to fix the problem.
Contact Microsoft if you have a non-English version of Visual Studio.