In a recent post to his blog Daniel Hofstetter talks about an issue you might been seeing with using the Google OpenID service and the PHP OpenID library.

It is possible that you get an “Invalid OpenID” error when you try to login with the Google OpenID (https://www.google.com/accounts/o8/id), or any other OpenID that uses “https”. In this case, the following steps might help to fix this issue.

He points out that you'll need curl and OpenSSL installed and set up to work with your PHP installation (ether compiled in or included as shared modules. Because of the change from the "http" to "https" format you'll need those two components to create that kind of connection.