Thank you for your reporting.
I'm not sure, but maybe you must specify variant type information
of arguments when you call PrintPostageEx.
I'd like to know what variant type of arguments is needed
to call PrintPostageEx.
What is the result of the following code in Ruby 1.9?

  method = internet_postage.ole_method("PrintPostageEx")
  method.params.each do |param|
    puts param.name + ":" + param.ole_type_detail.join(',')
  end

 Best Regards,
 Masaki Suketa