Error:A JSON text must at least contain two octets!

[mmuneer]

Hello,
I am getting the following runtime error when running the foursquare example app from my localhost:

JSON::ParserError in SessionsController#callback
"A JSON text must at least contain two octets!"
app/controllers/sessions_controller.rb:10:in `callback'

Here is the first few lines of the framework trace:
"json (1.5.3) lib/json/common.rb:148:in initialize'
json (1.5.3) lib/json/common.rb:148:innew'
json (1.5.3) lib/json/common.rb:148:in parse'
quimby (0.4.5) lib/foursquare/base.rb:91:inaccess_token'
actionpack (3.0.3) lib/action_controller/metal/implicit_render.rb:4:in send_action'
actionpack (3.0.3) lib/abstract_controller/base.rb:151:inprocess_action'
actionpack (3.0.3) lib/action_controller/metal/rendering.rb:11:in process_action'
actionpack (3.0.3) lib/abstract_controller/callbacks.rb:18:inblock in process_action'
activesupport (3.0.3) lib/active_support/callbacks.rb:435:in _run__434586317__process_action__929587020__callbacks'
activesupport (3.0.3) lib/active_support/callbacks.rb:409:in_run_process_action_callbacks' "

I have followed all the instructions in readme.md and still no results.
My callback url is: "http://localhost:3000/session/callback".

Any comment/ guidance will be really appreciated.

Thanks,
Muntasir