Steph Locke notes that there was a bug in the R 3.4.0 for Windows installation executable:
If you’re getting the following error when you’ve installed R 3.4.0 on Windows, you’re not alone.
Error in if (file.exists(dest) && file.mtime(dest) > file.mtime(lib) && :
missing value where TRUE/FALSE needed
Read on for the solution.