From: Junegunn Choi <junegunn.c@...>
Date: 2011-11-28T00:06:54+09:00
Subject: Re: Create Excel Sheet(.xls/.xlsx)

Which version of Ruby are you using?
If it's not 1.9.x, try loading rubygems first

require 'rubygems'
require 'spreadsheet'

-- 
cheers,
junegunn choi.