Gem install gets SSH certificate error

I am trying to install sinatra, on Windows 7 but get the following:

J:\DYNALT\ProgramData

ruby -v
ruby 2.0.0p247 (2013-06-27) [x64-mingw32]

J:\DYNALT\ProgramData

gem update --system
Latest version currently installed. Aborting.

J:\DYNALT\ProgramData

gem install sinatra
ERROR: Could not find a valid gem ‘sinatra’ (>= 0), here is why:
Unable to download data from https://rubygems.org/ -
SSL_connect returned=1 errno=0 state=SSLv3 read server certificate B:
certificate verify failed
(https://s3.amazonaws.com/production.s3.rubygems.org/latest_specs.4.8.gz)

How do I fix this?