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