WordPress 3.1 was one of the major release of WordPress and it introduced many new features and enhancements. But when it went live, many people reported small bugs or issues with it. An updated version was expected long time back and finally WordPress team rolled out WordPress 3.1.1 which fixed lots of bugs and improved security.
According to official announcement post, WordPress 3.1.1 fixed media uploader security issues, prevents potential PHP crashes caused by complex hyperlinks and corrects minor XSS flaw on database upgrade screens.
So, upgrade your WordPress blog to 3.1.1. and if you need professional assistance with upgrading WordPress, you can always hire me via our WordPress upgrade service page.