when you are behind a firewall and try to install ruby:
$ rvm install 1.9.1
Installing Ruby from source to: /home/chris/.rvm/rubies/ruby-1.9.1-
p378
Downloading ruby-1.9.1-p378, this may take a while depending on your
connection...
curl: (7) couldn't connect to host
just add to ~/.curlrc your proxy setting:
e.g.
$ cat ~/.curlrc
proxy = example.proxy_name.com:80
thanks,
chris