Symantec recently pushed out a signficant product update for both its Norton Antivirus 2011 and Norton Internet Security 2011 products, bringing the version number to 18.104.22.168. Among the upgrades are a few new features (like support for Mozilla's Firefox 4 browser), performance enhancements, better compatibility with third-party programs, and a handful of bug fixes.
According to BetaNews.com, the update also fixes an annoying issue where upgrading from a previous version of Norton could potentially result in a loss of subscription days being reported. Other tweaks include an improved activation process and better performance from Internet Explorer 9.
The new version is being pushed out automatically via LiveUpdate, though you'll want to check to verify it's been applied (Support > About). On one of our personal machines, we had to manually run LiveUpdate before it Norton would prompt us to restart our PC to apply the update.