My first doubt is about the element locator.
Can you test them using Selenium IDE or Firebug?
Also I suppose at this stage you would not be able to execute WebDriver code directly in Selenium IDE. Looking at the error message it seems that you may have to select some frame before proceeding these steps.
About new row id, I need to see the html of new row id to be able to guide on this.
~ seleniumtests.com