Connecting to VPN I get - Error 651: The modem (or other connecting device) has reported an error

Solution 1:

One suggestion I might have is to go to your Device Manager and click on View > Show Hidden Devices. Then in the "Network adapters" drop down you should see a bunch of WAN miniports.

There is a method for removing and then re-adding the miniport(s) that might be giving you trouble. I had a similar issue when trying to use an SSTP VPN, and removing + reinstalling the SSTP Miniport solved the problem. Not sure if it will work for you, but it is something that's not on your list of things tried yet ;-)

Here's some additional info: http://forums.techarena.in/vista-hardware-devices/982266.htm

Solution 2:

I had a very similar problem - posting my resolution here in case in helps anyone else. In my case I had VirtualBox installed and after several uninstallations/re-installations I was able to confirm that the specific cause of the VPN problem was the "VirtualBox Bridged Networking Driver".

To get the VPN working again without uninstalling VirtualBox (since I still use it!), I had to go to Network Connections and on the main network adapter, select Properties and then uninstall the VirtualBox Bridged Networking Driver. Deselecting it was not enough, the driver had to be uninstalled. After this my VPN worked perfectly again.

If you haven't got VirtualBox installed, it might still be another similar driver which is causing the problem, so have a look to see what other ones are installed in the network adapter Properties. Just make sure you have easy access to the driver files locally before you uninstall any, just so you can add them back easily if they are not the culprit.