Visitors to my clients web sites may have less than 1024x768 or 800x600 screen resolution, so it's imperative that this scrolling issue is resolved. Apparently, this horizontal scrolling issue is not limited to just Mozilla's Firefox browser. The web content that extends off to the right on Mac Safari (latest version) is also blank when scrolling right. I did not test IE, but assume the results are the same. Just make your browser window smaller than the template content, then scroll to the right. Again, this issue does not appear with WordPress templates, just Joomla/RocketTheme. What's WordPress doing right? Is it a CSS issue?
Specifically, check out your Akiraka template demo and the content in the greenish main body area. But other templates behave the same way and should not be hard to demonstrate the issue.