With OpenVPN 2.0.9, I receive the following error when running the server in bridged mode under Windows 2003 Standard SP1:

Mon Dec 18 19:11:25 2006 NOTE: could not get adapter index for \DEVICE\TCPIP_{F6 544727-8E1F-495D-BBCE-97FCDC2D45AE}, status=55 : The specified network resource or device is no longer available.

At this time, I have found no solution to the above issue, though I have found more information about the error on the OpenVPN mailing list archives:

When you set up a bridge, generally the adapters which are components of the bridge adapter lose their individual configurations — only the settings on the bridge adapter itself are relevant.

When you run OpenVPN on a bridge adapter, you should manually set the IP address and netmask of the bridge adapter, then run OpenVPN with –server-bridge or if running in point-to-point mode, omit –ifconfig.

Thus, as long as everything appears to work, you can safely ignore this message.