This bug is in the wix200x.targets (and possibly the wix2010.targets) file. It occurs only if Cultures are operating. The @(SignTargetPath) ItemGroup, resolves to a path without the current Culture in it, whereas the signing targets are beneath a Culture qualified path.
i.e.
D:\Build\Debug\x64\en-us\MCTestDeployment1.0.msi
D:\Build\Debug\x64\MCTestDeployment1.0.msi
So I'm seeing errors...
2011-12-09 04:23:43 PST in Windows Installer...
