A library (reported by .libPaths()) that was available when affy was installed is no longer available. Maybe you installed a new R over an old R? You could try to re-install packages biocLite("affy") or trouble-shoot on your end how the libraries that were there when affy was installed originally are no longer available. Be sure that BiocInstaller::biocValid() reports that packages are current; likely you have a mix of packages for different R and Bioconductor releases.