It's not a perfect system so sometimes you have to give it a nudge. I have just installed Crypt-DES from the University of winnepeg using the command line.

ppm3 install http://theoryx5.uwinnipeg.ca/ppms/Crypt-DES.ppd
[download]

I had previously tried the ActiveState directory and didn't get anywhere. The approach to take is to install (or just view) that latest PPM::Repositories and use alternate repositories when a specific install fails. Don't be afraid to add and delete repositories.