localRepo

Man... what a hassle!

Why do I bother checking "specific version" if Visual Studio just copies a different version over the top? Maybe it's MSBuild that's doing the copying.

The secret is that the wrong version of the assembly gets cached here (on my vista box, it may be different in XP):
~/AppData/Roaming/localRepo/Cache/wrongDllVersion.dll

I found the path by checking "read only" on the DLL that kept getting overwritten with the wrong version. When I built the project there was a warning about how Visual Studio was unable to copy the dll.

HA! Take that, Visual Studio!

Sorry if you don't care about DLLs or Visual Studio; I had to put this up so I can find it next time I google: ".net dll wrong version cache"...