wrong number of arguments (0 for 1) when calling 0 argument web service call

I created a Ruby client using the following command:
wsdl2ruby.rb --wsdl https://fba-inbound.amazonaws.com/doc/2007-05-10/FBAInboundService.wsdl
--type client --force

Here is how I call the service:

@service = SOAP::WSDLDriverFactory.new(wsdl).create_rpc_driver
@service.generate_explicit_type = true
@service.wiredump_dev = STDOUT
@service.endpoint_url = url

begin
    result = @service.GetServiceStatus()
rescue Exception => ex
    puts "Caught an exception:\n#{ex}"
end

Here is the relevant part of default.rb (generated by the above
command):
# {http://fba-inbound.amazonaws.com/doc/2007-05-10/}GetServiceStatus
  class GetServiceStatus
    @@schema_type =
"GetServiceStatus"
@@schema_ns = "http://fba-inbound.amazonaws.com/doc/
2007-05-10/"
@@schema_qualified = "true"
    @@schema_element = []

def initialize
    end

end
  # {http://fba-inbound.amazonaws.com/doc/
2007-05-10/}GetServiceStatusResponse
  class GetServiceStatusResponse
    @@schema_type = "GetServiceStatusResponse"
    @@schema_ns = "http://fba-inbound.amazonaws.com/doc/2007-05-10/"
    @@schema_qualified = "true"
    @@schema_element = [["getServiceStatusResult", [nil,
XSD::QName.new("http://fba-inbound.amazonaws.com/doc/2007-05-10/",
"GetServiceStatusResult")]], ["responseMetadata", [nil,
XSD::QName.new("http://fba-inbound.amazonaws.com/doc/2007-05-10/",
"ResponseMetadata")]]]

    def GetServiceStatusResult
      @getServiceStatusResult
    end

    def GetServiceStatusResult=(value)
      @getServiceStatusResult = value
    end

    def ResponseMetadata
      @responseMetadata
    end

    def ResponseMetadata=(value)
      @responseMetadata = value

end
    def initialize(getServiceStatusResult = nil, responseMetadata =
nil)
      @getServiceStatusResult = getServiceStatusResult
      @responseMetadata = responseMetadata
    end
  end

When I run this I get:
Caught an exception: wrong number of arguments (0 for 1)

Also, when I try to get clever and call it as follows:
result = @service.GetServiceStatus(nil)

I can see the response from the web server, but I get the following
exception (I believe this is thrown when creating the
GetServiceStatusResponse object as the "result" variable above is
nil):
Caught an exception: private method `sub' called for nil:NilClass

Calls to other methods which have at least one argument work, but I
cannot successfully call this 0-argument method and get back the
response.

Any help is appreciated.

Thanks.
Eric

This would probably be more appropriate for the ruby-talk mailing list.

Regards,
Michael Guterl