Hi Eli,
The reason you are receiving this error is because eBay just imposed new maximum shipping cost rules for items listed in the "media" categories. As a result of this change, when listing in the "media" categories, your least expensive domestic shipping service cannot exceed $4.00.
If you would like to read more about this new policy, I recommend checking out the following page of eBay's help index: http://pages.ebay.com/sell/August2008Update/MaxShipping/
If you have any additional questions or concerns regarding your Auctiva account, please feel free to contact our customer support team using the web form on the following page: http://www.auctiva.com/help/requesthelp.aspx
-Mike