Some games (most notably Star Wars: The Old Republic) run as an admin on your computer. To use Ventrilo properly with it, you will need to run the Ventrilo client as an administrator as well.

You can do this each time you run Ventrilo by right-clicking and selecting ‘Run As Administrator’, or you can set it to always run as an administrator by right-clicking, selecting ‘Properties’ and, on the Shortcut tab, clicking the ‘Advanced’ button. There will be an option to always run it as an admin.