It seems I cannot install the current version of OpenVPN (2.1.2) because the TAP driver is not signed and therefore windows 7 x64 refuses to install it.
It shows up in the device manager, but with a yellow exclamation mark.
It's a fresh system, and OpenVPN was never installed before.
When I start the OpenVPN client it seems to connect fine, but then it stops with
CreateFile failed on TAP device: ... All TAP-Win32 adapters on this system are currently in use.
How can I install the unsigned drivers, or are there signed drivers available somewhere ?