After some major troubleshooting, I figured out how to get ROTOR (the "shared source" version of Microsoft's .NET framework) to build. As it turns out, the build scripts rely on the old school 8.3 DOS-compatible filenames, which I had turned off long ago. It was attempting to compute the INCLUDE_PATH, and was choking since the path it came up with did not exist. After some filesystem trickery, I gave my Visual Studio installation an 8.3 filename and voila! It is building as we speak. It took quite a while (several hours) to compile on Dave's iMac, so we'll see how my PC fares. (Not a PC vs. Mac argument)