1. Close the Desktop App completely (make sure that it's not still running in the System Tray or the Dock).
2. Install the latest version of the Flash player: http://get.adobe.com/flashplayer/
3. Restart the Desktop App.
4. If that doesn't work, uninstall Adobe AIR:
To uninstall Adobe AIR on Windows:
a. Select Start -» Settings -» Control Panel.
b. Open the Add or Remove Programs panel. In Windows 7, you may have to change the View menus to show Category to see this.
c. Select Adobe AIR to remove the runtime.
d. Click the Change/Remove button.
To uninstall Adobe AIR on Mac OS, double-click the Adobe AIR Uninstaller (Adobe AIR Uninstaller.app) in your Applications/Utilities folder.
5. Uninstall the Desktop App.
6. Reinstall the Desktop App (if the Install Now link does not work, then try the Manual Installation): http://www.pandora.com/desktop_app
* In Mac OS X, if you have Latin America Spanish enabled in International Settings, this may cause problems with the Adobe AIR application. Please remove it from your language list and use Español (Spanish) instead.
Adobe AIR Support: http://kb2.adobe.com/cps/403/kb403150.html