I recently decided to build a virtual machine with Ubuntu 8.10 to test most of the tools I use before upgrading my main laptop with it, and what do I find? that it is using Ruby 1.8.7 without the patch provided by HD to Ruby to fix an error on the use of Shortnamed Variables. So guys I recommend if you use Metasploit not to upgrade to Ubuntu 8.10 just yet, I'm also getting errors with Nessus.

HD has posted a bug to Canonical and it appears they are working on it for more info

https://bugs.launchpad.net/ubuntu/+source/ruby1.8/+bug/282302

Shell is Only the Beginning

Ruby in Ubuntu 8.10 Broken for Metasploit use