NPanday should be built using x86-toolsets of the .NET Framework - the build will succeed, but tests will fail, if built with Framework64. On 64bit operating systems, however, NPanday defaults to Framework64. The easiest way to workaround the issue, is to change the file path for all frameworks in .m2\npanday-settings.xml.
We expect to enable native support for building with 32-bit even on 64-bit operating systems in the next version of NPanday, though. For Details see NPANDAY-369.