I got build failures with the version of "microsoft.vssdk.build.tasks.dll" in CVS. This may be because I am using VS2008 SP1 but it may make sense to update to the newer version or reference the on in the VS folder.
I copied the files from "C:\Program Files\MSBuild\Microsoft\VisualStudio\v9.0\VSSDK". The dll file version is v9.0.21119.0.
On futher investigation it appears that this file is actually not a valid DLL, it doesn't contain any version information and seems to be mainly full of nulls.