Google Analytics Multiple Domain Tracking and Ecommerce Code

We have an established ecommerce website linked to a third party hosted shopping cart and payment gateway. We have Analytics installed on our site and linked to Adwords, Adsense and Webmaster Tools. However, we are havoing a problem with Ecommerce reports in Analytics. We can see transactions in our reports (product name, SKU and price) but we are not getting any source/ medium information about purchasers which is obviously quite a critical part of the ecommerce reports.

We are not sure if our implementation/ code for tracking over multiple domains is incorrect or whether our third party shopping cart (romancart) is not managing the information correctly.

We would like an Expert in installing Analytics for Ecommerce across multiple domains to look at our code and implementation to confirm whether it is set up correctly or not - and if not, advise us on what changes to make. We can provide access to our analytics account as required.