When you upgrade, you upgrade the entire Vicidial installation, not just the agent screen. The agent screen contains software that must interact with the rest of the system, and must therefore be in sync with the version or it won't work.
Note that you have installed Vicidial using the Goautodial installer. There is also an installer named Vicibox (at vicibox.com) which installs the latest version of Vicidial available at the time of the installation. It can be easily upgraded at any time (literally, any time you get bored you can upgrade to get the latest bug fixes and features). You can also back up your present Vicidial Database, install from the Vicibox installer, and then restore your DB into the new server and upgrade the DB to match the latest version of Vicidial you have just installed. Instructions are in /usr/src/astguiclient/trunk/UPGRADE on every Vicibox installed server for how to upgrade the DB.
Also worthy of note, Vicibox installs Stock Vicidial and is supported by The Vicidial Group (and every Vicidial professional). Goautodial is supported by a smaller group of specific professionals and specifically is not supported by The Vicidial Group (in addition to being an older version of Vicidial, and missing features as a result!). Goautodial is very useful if your enterprise requires CentOS, as it is quite stable (if old, missing features, and having a few design flaws that can disable and/or hide certain features). On a lighter note: Goautodial *also* installs the stock Vicidial system, but does not show you the links to it. So you need only find those links and you CAN use stock Vicidial in a Goautodial installed system. Additionally, that stock Vicidial CAN be upgraded in place to the latest version of Vicidial, although doing so will irreparably break the Goautodial-modified interface. Still very useful if you must have CentOS, solid install.
that being said: To upgrade your Goautodial Installed version of Vicidial, there is a wiki available on Goautodial.org. This will allow you to upgrade your entire installation to a later version of the Goautodial installer. It won't give you the Latest version of Vicidial, but it will be more recent, and will give you the latest version of Goautodial with a newer web interface.