So there appears to be significant enough changes in Vista that it breaks OpenVPN in a few ways, one of which is that OpenVPN can’t insert routes into the Vista kernel routing table. One ( untested by me ) workaround is to use the following to items in your config:
route-method exe
route-delay 2
Also, you need to create a batch file launching openvpn with it’s config file and then ‘run as admin …’
The other option is to use 2.1rc4 which incorporates changes to be more compatible with Vista. Once again Vista breaks things and others need to change to support it.