Hi Andrew I had the same issue. This is what I did
Download the source from “http://search.cpan.org/CPAN/authors/id/D/DA/DAVECROSS/Calendar-Simple- 1.21.tar.gz“ Extract the tar file, change to the extracted dir # perl Makefile.PL # make # make test # make install Then make fixdeps restart your web server then try again Discover RT's hidden secrets with RT Essentials from O'Reilly Media. Buy a copy at http://rtbook.bestpractical.com