Flagship Industries, the makers of the popular Voice Software Ventrilo, released Ventrilo 3.0 today. This version is not backwards compatible with previous versions, therefore if you run version 3.0 of the server software, or your host is running version 3.0 of the server software, you must upgrade your client software. Luckily if you have no clue what this mean, just keep on using Ventrilo as normal. If you login to a new version of the server, the old software will display a "version mismatch" error.
Grab the latest version of Ventrilo here.
http://www.ventrilo.com/download.php