If you are getting something like the following, on a box without ipv6 connectivity:
/opt/rbenv/versions/1.9.3-p547/lib/ruby/gems/1.9.1/gems/excon-0.44.4/lib/excon/socket.rb:291:in `raise_timeout_error': read timeout reached (Excon::Errors::Timeout)
from /opt/rbenv/versions/1.9.3-p547/lib/ruby/gems/1.9.1/gems/excon-0.44.4/lib/excon/socket.rb:49:in `rescue in readline'
[...]
from /opt/rbenv/versions/1.9.3-p547/lib/ruby/gems/1.9.1/gems/fog-core-1.29.0/lib/fog/core/connection.rb:81:in `request'
from /opt/rbenv/versions/1.9.3-p547/lib/ruby/gems/1.9.1/gems/fog-1.28.0/lib/fog/rackspace/service.rb:42:in `request'
from /opt/rbenv/versions/1.9.3-p547/lib/ruby/gems/1.9.1/gems/fog-1.28.0/lib/fog/rackspace/storage.rb:444:in `request'
from /opt/rbenv/versions/1.9.3-p547/lib/ruby/gems/1.9.1/gems/fog-1.28.0/lib/fog/rackspace/requests/storage/put_object.rb:35:in `put_object'
from /opt/rbenv/versions/1.9.3-p547/lib/ruby/gems/1.9.1/gems/fog-1.28.0/lib/fog/rackspace/models/storage/file.rb:270:in `save'
from /opt/rbenv/versions/1.9.3-p547/lib/ruby/gems/1.9.1/gems/fog-core-1.29.0/lib/fog/core/collection.rb:51:in `create'
from ./jekyll-cloudfiles-upload/cloudfiles_upload.rb:79:in `block in <main>'
from ./jekyll-cloudfiles-upload/cloudfiles_upload.rb:77:in `each'
from ./jekyll-cloudfiles-upload/cloudfiles_upload.rb:77:in `<main>'
then you need to tell to fog to prefer ipv4 with:
connection = Fog::Storage.new(
:provider => 'Rackspace',
:rackspace_api_key => '<my api key>',
:rackspace_username => '<my username>',
:rackspace_region => :dfw,
:connection_options => { :family => ::Socket::Constants::AF_INET }
)