I think I misunderstood the (English) meaning of the error message.
When it said it “cannot be read from a file”, I though it meant “I cannot find the file”.
I did a little more digging around and found that the openvpn binary (on zeroshell) would have to be built with the “–enable-password-save” option in order to accommodate what I want to do, but that’s not the case so I’ll have to find another way to do what I want.
Thanks.
(see http://openvpn.net/archive/openvpn-users/2005-01/msg00349.html )