This solution applies to all Barracuda SSL VPNs, using Network Connect on a Mac with a new Snow Leopard install.
When Snow Leopard is installed on a Mac it removes the Network Connect tap driver. This means the client software is still installed but has no way of connecting to your Barracuda SSL VPN. To correct this issue, you will have to reinstall the Network Connect Client from the Barracuda SSL VPN interface as this will reinstall the tap driver.
Navigate to Resources > Network Connect on the Barracuda SSL VPN. Click on Download Mac Client and reinstall Network Connect.
Link to this page: