I'm the CEO of Deterministic Networks, Inc. Apparently the Flightline VPN includes one of our components called DNE (I suspect they OEM the VPN client from one of our customers). Unfortunately, from a recent support request, I note that it has a very old, pre-Vista version of DNE included. Also, a few weeks ago, Microsoft issued a Windows Update for Vista which now blocks early versions of DNE on Vista. They were supposed to only block new installations of old versions of DNE, but they chose to also block working versions of DNE which interrupts network connectivity. We're working on resolving this with Microsoft.
In the meantime, you can likely get your VPN clients working on Vista if you download the DNEUpdate from the lower right of our homepage at www.deterministicnetworks.com. If you don't have the product already running on Vista, install the DNEUpdate, then install the VPN client - it will work with a newer version of DNE.
If you have questions, you can contact us through the support form on our website. You will usually get a response within a few hours.
Steve