Phoenix Viewer Team announced that they stop the official support for V1-based Phoenix Viewer at the end of the year 2012. They are also no longer developing this viewer for Second Life.
If you use Phoenix Viewer they recommend to migrate to Firestorm Viewer (file named Phoenix-Firestorm). But they aren't forcing you to use that other viewer, even you can continue using Phoenix Viewer because they won't block it from logging in. But you have to know that it will become more and more deprecated over time.
They also tell that they will remove the download link to Phoenix Viewer on their main website in 2013, but it will remain available from their "Other Downloads" section of their wiki. However, they won't remove any documentation or JIRA issues reported against Phoenix.
For more information, please check the official Phoenix Viewer Team Website: http://www.phoenixviewer.com/