It's only been a few days since the 0.5 release but I've been busy updating CryptoNark with some bug fixes and also added in support for Windows. One caveat: I've only tested this on WIndows 8.1 under a Strawberry Perl 5.18.2 installation. Please let me know if there are any issues on older/newer versions of Strawberry Perl.
One additional item to note in this version. SSLv2 connections to some sites were causing perl to crash when running on Windows. I've modified the subroutine that is making SSLv2 calls to make it more stable but on those sites that it was crashing on, cnark now falsely (?) reports that an sslv2 connection with an RC4-MD5 cipher is possible. I'm still investigating this issue. It does not happen on all sites.
You can download the new CryptoNark v0.5.5 release from the Downloads page and you can see the changelog at the CryptoNark page on this site.