I fixed it with:
require 'win32console' if RbConfig::CONFIG['host_os'].include? "mingw32"
I didn't know that I had to use "win32console" gem with a cygwin terminal even in the case that I I am not outputting colors as so far I have been using "win32console" only togheter with "colorize" gem to make colors work in windows xp native command prompt.
I'll stick a reminder for this at the top of my code...