I should probably add that when I first encountered this issue, I did not have the XRDS-Simple plugin installed. I have since added it in hopes of fixing the issue, but it didn’t help. I’m not entirely clear on what XRDS is for, but the OpenID plugin suggested that it was needed for some functionality.
Also, I’m running PHP 5.0.4. From what I’ve found so far, the first two warnings are related to that, but should not terminate the script. So apparently it’s the third one that’s causing the problem?