Cannot make rails app in my directory

i have problem when try create new apps in rails,
i type rails new coba, then the respon is

Fetching source index for
Using rake (
Using i18n (0.6.0)
Using multi_json (1.3.1)
Using activesupport (3.2.1)
Using builder (3.0.0)

Gem::RemoteFetcher::FetchError: Errno::ETIMEDOUT: A connection attempt
failed because the connected party did not properly respond after
a period of time, or established connection failed because connected
host has failed to respond. - connect(2) (
An error occured while installing activemodel (3.2.1), and Bundler
cannot continue.
Make sure that gem install activemodel -v '3.2.1' succeeds before

HELP ME please