Visual Studio 2008 installs .NET 3.5 SDK v6.0A, which is what NAnt 0.86 expects to run against – however, the .NET 3.5 SDK that is available for download, via the "Windows 2008 and .NET 3.5 SDK", is v6.1. 

It’s a small difference, but that difference will cause NAnt 0.86 to not be able to target .NET 3.5 if you are using the downloadable .NET 3.5 SDK. When you try to run NAnt 0.86 and have it target .NET 3.5 with the downloaded .NET SDK, you will get an “Object reference” error from NAnt and the build will fail immediately.

Page Brooks has the details of how to fix NAnt to work against the v6.1 SDK. It is an easy fix, but it requires that every machine running NAnt have the v6.1 SDK installed (and if you want your devs to be able to run NAnt from their local machine, you’ll need all of the developers to install the updated version of the SDK).

End Result:

If you want to automate your VS2008 project builds with NAnt, you should probably have every developer on your team to install the new version of the SDK and have NAnt target that version.