I'm following the Simply Rails 2 book but am having an issue with the Ruby Gems aspect. After some research I found out that the place to get gems is now gemcutter.org, NOT rubyforge.org. I am running Leopard, so I'm not sure if the gems release was already on here or if it was installed by following the book instructions.
I ran the following commands as instructed by page 27 of the book.
GemCutter is a new resource and has only become prominant fairly recently. Certainly well after the SitePoint book was published. However, it hasn't replaced RubyForge, but rather it has taken over some of RubyForge's preeminance as the main gem repository. More information here:
In other words: gem update should work for RubyForge. You just might not get some of the very latest versions of some gems.
Therefore, I don't think your problem is with the site but your system. Possibly a bug in your gem install. However, I'd start by checking your firewall rules and that you have external connection rights from the console. Unfortunately my Mac knowledge isn't great so I can't tell you where to look for these.
So, it was bugging me so much I just kept at it and finally got something to work. I kept reading that there was possibly a bug somewhere in the gems version installed on this flavor of OS X. I ended up going and getting the latest version of rubygems from rubyforge and put the folder in the same directory as the version that wasn't working. I ran the same commands from the book but referenced the new folder and version. The install went fine.
gem -v is returning 3.5.4 as it should.
I also set my rails config to start looking at gemcutter for new gem updates. Everything seems to be working great now.