Well, in the interests of due diligence, I checked out & built each of the four flavours (32/64 Release/Debug) independently and without any errors. I then rebuilt each with the "wrong" Platform (ie for Win32 in the x64 directory and vice versa) without cleaning first and also without error.

So I'm going to close this on the ground that we can't reproduce it. If someone can come up with a recipe for reproducing the problem we can re-open (or start a new issue).